u/Difficult_Shame_1186

I played this game,and watched Japanese streamers play it and reading lines ,and with help of my knowledge of Japanese,and some translating,I managed to get the main story of this game almost completely right. I did something similar many years ago,but it was much shorter,and more innacurate. This is only for main story(it's quite long):

At the beggining,you(player) are greeted by Babamon,standing in empty black background (similar to Jijimon in Digimon World). She asks for your real full name,and date/year of birth (very personal). She goes on about choosing you to save a Digimon world, File Island,in which matters are settled through Card Battle,from an extreme danger. You are also given a matrix of a certain 'Legendary Hero'(Digimon World protagonist) for you to appear in a Digital World (She says even if you're a woman,or the old man,you will look like that boy). After you choose your name for digital world (seriously,what was the point of asking my real name and birth date),Babamon lets you choose one of three legendary ancient Hero decks, carved in stone,to be your starter deck. She then transports you to File Island,where Babamon resides.

You find yourself in the Village of Begginings (File City),center of File Island,and go meet Babamon,who presides over it. She welcomes you as 'Legendary Hero' and explains the Island danger to you. Recently,a certain Bug card,has been excavated in Ancient Dino Region,and that started to cause 'bugs' all over File Island.From small glitches,to serious life threatening illnesess. Such cards appeared before,but never of such magnitude. Card Leader of that region Brachiomon contacted Babamon about it,but before she could act,Bug card incapacitated Babamon to leave File City. Therefore,it is your mission to travel the File Island,and collect seven most powerful cards, 'Sevens Cards' each held by it's respective Card Leader of a certain region:

Angemon – Freezeland
Brachiomon – Ancient Dino Region
Hououmon(Phoenixmon) – Great Canyon
Jyureimon(Cherrymon) – Misty Trees
Panjyamon – Gear Savannah
Scumon Daiou(King Sukamon) – Dust Kingdom
Vamdemon(Myotismon) – Overdeel

When collected,those cards grant access to Mugen Mountain(Mt. Infinity),where main control system of the island is located,and where effects of Bug card can be fixed. There is also another big problem. Bug card has been stolen. Babamon has given the task to Andromon to conduct a search for it. Since she's old,Babamon takes several breaks when speakin for so long. She sends you to Green Gym,where you meet her lively and cute friend Betamon,who teaches you basics of Card Battle,and tells you about surrounding areas to start your jorney. He also tells you how he and Babamon (which doesn't like to be reffered to as old) recently travelled to Ancient Dino Region,where he picked up an unusual rare card,but incoming storm blew it away from him. Betamon promises his new friend (you),that if he ever finds rare card he will give it to you. Babamon also gives a Digivice(Adventure model),so called 'proof of Legendary Hero' to show it to Digimon to trust you.(which has no real gameplay purpose,other than for story,and viewing some player stats),and some money for your travel and Card Shops,and your embark to your journey. In which,if your lost,you can come to Babamon which will predict where you need to go,as well as your progress on Sevens cards.

When you exit the City,and enter Unwavering(Native) Forest,you,are startled by a wild (because of Bug Card) Agumon,who wants to fight you. After defeating him,he regains his senses,and tells you about a now closed DigiBridge,which leads to Tropical Jungle. On the bridge,you fight Kunemon guarding it,who tell that his friend Gabumon,who manages the bridge is missing. You see weird Gabumon's note,which says (Don't search for me,dori). You go to Coela Point,where residing Palmon fights you,and tells you she saw Gabumon going away with some weird Digimon with drills on their heads. You also see a sign for 'Ferry Digimon giving tours to see Digi-Corals'. But that's for another time. Anyway,you come to Drill Tunnel,and find out a suspicious Drimogemon couple kidnapped Gabumon. You fight them,and rescue Gabumon,and they admit to have kidnapped Gabumon,because they lost their business in Tunnel,since people(Digimon) stopped passing through it,becuse of Miharashi Mountain(Mt.Infinity) has been closed,and Drimogemon suspected it was fault of their travelling competition, Gabumon of Digibridge. Gabumon returns and reopens the bridge.

Deeper in Drill Tunnel,in Lava Cave,you find Meramon,severely weakened because rocks have blocked flow of lava,which Meramon suspect is the fault of Unimon from Mt. Miharashi. Meramon the clears a path to Miharashi for you to go but on the way,you are blocked by a weird Goburimon Trio,which demand money from you. After beating them,you arrive at Unimon,which doesn't trust you,and after a battle she denies culpability,blaming Meramon instead,while showing the trees of Mountain withered. She also said that Meramon was seen returning from Ancient Dino Region recently,where all the Bug trouble has begun. You later go to Tunnel's underground lake,where you find a Tankmon taking a bath in oil. He says he came all the way from Misty Trees,when a certain group of Agumon attacked him. Also,they're suspect of destroying toilets around island. Tankmon hid,and found a toilet there,and blocked lava flow with a rock,to make himself fell less hot. He removes the rock,you give him some money for travel,and he gives you bottle of oil which Meramon asked you to bring him. You find a collapsed Meramon,and spill oil on him to regain his strenght. After he thanks you,he gets angry at you for asking about his trip to Dino region,and fights you. After that,he explains that he was actually in the Overdell to visit his old friend Vamdemon(Card Leader). He says Vamdemon is good guy,but started acting strangely,and even said 'Something horrible will happen on this island',which worried Meramon. You go to Unimon to explain it,and she reopens a path to Gear Savanah.

After coming to Tropical Jungle via DigiBridge,you go to mangrove woods,where Vegiemon,asks to give it a Rare type card to pass,after giving it,she points you to Amida Forest,which leads to Ancient Dino Region. Guardian of forest,Centarumon fights you,and after win,and showing him Digivice he lets you into severely emporished Ancient Dino Region. There, underlings of Brachiomon fight you,even with you showing Digivice. First, you fight Monochromon,who tells you about Vamdemon's bodyguard Vermillimon,who was seen spying in the area. In Bone tunnel,you fight Tyrannomon,who lets you see Leader,huge Brachiomon. He doesn't really trust you,calling you'fake hero'. He also says it is Vamdemon's fault for whole Bug situation,especially in ADR. He tells you he'll give you his Sevens card,if you find and bring him Bug card. You then go to Overdell,where SkullGreymon,new bodyguard of Vamdemon,informs you Vermillimon was seen in Great Canyon,although you don't find him there(although there is a tense looking Monochromon in card shop). In Overdell Cemetery you fight Bakemon who guards it,but key to Vamdemon's Mansion is gone, You go Dragon's Eye Lake in Native Forest,where Bakemon was playing,and lost it. There,Igamon(Ninjamon) found it,and won't give it without a fight. He says that he came here from Gear Savannah to train,and run away from annoying Patamon who challenges everyone to fight. After entering Grey Lord's Mansion,Vamdemon's ally(not servant he said) Devimon challenges to card fight,and after it,you're granted audition to Vamdemon himself. He appears normal,and denies his connection with Bug incident,and blames Brachiomon instead. He also says he'll give you his Sevens card,if you find,and bring him Bug card. Just like Brachiomon. What to do?

In Gear Savannah, aformentioned lively Patamon pesters you into battle, and later tells you about Agumon 'Yattarude' gang being stationed in Savannah. You come to Card Leader Panjyamon,who always trains,and asks you to bring him 100 rolls of toilet paper,because toilets are being destroyed,and paper is missing. He suspects it's the work of Agumon gang. When you bring him toilet paper,he'll give his Sevens card.When come to base of naughty Agumon's (all with numbers on their heads),they won't let you to see their leader without membership card. You find one dropped by Goburimon gang,in place you fought them. Then,you meet the leader,the notorious Führer (総統) Agumon(Yes,that's literal translation),who you fight. He denies being involved in toilet breaking incident,and 'predicts',that File Island will soon perish because of recent incident,and he gathered 'chosen group' of his kind stand a top of Island. He also predicts something important happening in Factorial Town,which is our next destination.In card shop,you talk to Elecmon,who tells you that gate to FT,is closed,and can only be reached by the ocean. Also,Piyomon tells you about fake battle cards circuling around recently. You return to Coela Point where you talk to Palmon about Coelamon,fish Digimon who likes taking people on his back to travel sees,being inspired by Whamon.But,he had a certain bizzare accident when a huge frog Digimon Coelamon was carrying,injured him because of weight,which Palmon finds kinda funny. You found Coelamon recovering at the Naked Beach, which is reluctant to take you,but after a fight, he agrees. He takes you(with great effort) from Coela Point to Factorial Town's square,where you open a town's gates. You enter a factory where Fugamon ambushes you for breaking and entering. After beating him,you meet his 'Great Teacher' Etemon,who appears polite(albeit slightly arrogant),and denies his accusations of producing counterfeit cards in factory.In File City,Betamon is super happy for finding a rare card,which he gives you,as promised. Turns out,it's fake MetalGreymon card made by Etemon (with signature). You face him with evidence,before he attacks you,After winning,he is more than willing to cooperate. He was making fake cards from toilet paper,but he didn't steal it.It was given to him by KingSukamon,Card Leader,also responsible for breaking toilets with his Sukamon minions,something even Etemon dissaproves. When you confront KingSukamon,he won't stop,saying he'll give you his Sevens card,if you join him in toilet destruction. You obviously refuse,and he asks you to bring him 100 rolls of toilet paper. With Panjyamon's,it's total of 200 rolls. You ask Etemon to give 200 rolls,but only has 3 left. So, he points you to Misty Trees,beyond Geko Swamp,to get Paper Tree,necessary to make toilet paper.You also ask him to make you two fake Bug cards,for respective Vamdemon and Brachiomon. He agrees (and almost signs it).

With a dose of fear of being caught you go to give them 'Bug cards'. Brachiomon believes it and gives you his Grand Sevens card. Vamdemon as well,and gives you Dark Sevens card. He's really euphoric about finding Bug card,goes away,and tells you to 'be careful on the way out'. It quickly becomes clear when his bodyguard SkullGreymon ambushes you. After winning,he reveals Vamdemon put him to keep you from reaching him. He reveals Vermillimon is actually in Great Canyon and is in fact camouflaged as Monochromon in Card Shop. When confronted,he desperately fights you. After defeat,he tells you whole story. When Bug card first appeared,Vamdemon sent him to Ancient Dino Region to scout the area,as he suspected Brachiomon.He was spotted by resident Monochromon,but let him go since they're similar species. On the way back,he overheard Vamdemon and Meramon talking in Overdell. He was saying he will destroy File City,and reign terror over whole File Island. Vermillimon wanted no part in it,and got away.He thought you were Vamdemon's assassin,who was out for his head.After that,you hurry to File City,where Vamdemon awaits. He says Babamon took away 'his darling(honey)' from him,and in his desperation,he will wipe out entire File City with Bug card you gave him. When he fails,because card is fake,he angrilily turns at you for a Card Battle. After winning,he lost a will to live without his love,but then, a mysterious flowerhead-woman like Digimon suddenly appears. It is Vamdemon's darling. He is overjoyed.She whispered something to him,and he suddenly becomes friendly,and leaves city. Flowerhead Digimon dissapears,and Babamon returns. She says that's a Digimon she knows from before,and now that problem's settled,send you to retrieve rest of Sevens cards.

In Great Canyon,on Gre Bridge, you encounter Igamon,who trained,and wants a rematch with you. After that,he points you to Upper Area,where Card Leader Hououmon(Phoenixmon) resides,and says entrance to Freezeland is blocked by ice pillars made by Icemon on behalf of Card Leader Angemon. Hououmon is weakened by cold from ice,and says Angemon captured her underling,Birdramon,which is Hououmon's messenger.Since bridge is blocked,Hououmon takes you to Freezeland on her back. There,in Ice Sanctuary,Angemon says his Great Angel Statue ,made of ice,and passed on by generations,was stolen,and Birdramon was kept as a suspect. Angemon then lifts ice pillars for you to pass. You promise to find statue,and hear from Whamon at Iceberg Beach,that he heard suspicious characters,carrying some statue,and bringing it to their fort. That turns out to be notorious gang of Ogremon and his lackey Agumons hiding in their Great Canyon base. Ogremon denies it at first,but Agumon slipped a word about a statue. After a fight,statue is returned,and Birdramon released,which was also injured,and Angemon took care of her. You fight Angemon to get his Sevens card,Holy Sevens. In Upper Area Birdramon thanks you,and let's you see Hououmon,which recovered,and you fight her for Speed Sevens card.

Sometime during your search for Sevens cards,Betamon invites you to File City,for a big news. Babamon says that Andromon finished his search for Bug card. He said it is located on the last floor of Mt. Infinity. Babamon says that super poweful Digimon,Mugendramon(Machinedramon) lives there,and is probably main culprit. She say that 'game balance' of that world is pretty bad,and Mugendramon will be very powerful,and send you back to Sevens cards hunting.

While searching Factorial Town,you enter Trash Mountain,where you sense a horrible smell. Numemon residing there is insulted by that statement,and think smell is lovely. He fights you,and says that smell comes from Geko Swamp,area behind this one,and shows you the way. In Geko Swamp,Otamamon asks for help,because the smell of is unbearable,and also, trees of the Misty Trees closed up,not allowing smell to leave the area,which might be work of forest elder,and Card Leader Jyureimon.Otamamon points you further in area,where you see a Gekomon drunk on alcoholic sake,which smell spreads around. You enter Daion palace(Volume Villa),where a sole Gekomon guards the palace,and his master's treasure,thinking you're a thief. After you fight him and win, Gekomon,after failing his master,wants to do a sepukku (ritualistic suicide,they're really serious in this game),but you talk him out of it,and prove you mean well. He said since their lord,TonosamaGekomon dissapeared soon after Bug illness appeared,his people went desperate and lost,and started getting massively drunk on sake. You ask for photo,to recognise him when found,and after seeing picture from his young days(looks the same a now),you recognise him as huge frog like Digimon lounging at beach in Tropica Jungle. You go there,but lord won't move,so you Cardfight some sense into him. He agrees to return,after a quick pun (Kaeru ga kaeru-Frog is going back). Back in Villa,Gekomon is really greatful to you,and shows you to his lord. They show you a Tonosama's personal secret passage to Misty Trees,which you use.

In Misty Trees,fog is intense,and you trip on sleeping Shellmon,who gets angry and fights you,before calming down and point you to location of Paper Tree,Foot of Tree. There,asking for help finding it,you awake a Kokatorimon,which screws with you,saying he uses Paper Tree for a pillow,and refuse to give to you for the kicks. You then kick some sense to him by card battle.He gives you Paper Tree,and points you to Card Leader Jyureimon. In front of 1000-year old tree,you sneeze 3 times,and shall meet him. You do just that and he appears. He greets you,and knows all about you,Babamon (which most of the islanders don't recognise for some reason),and situation on island. He also says that forest is safe from Bug card effects,because forest itself is capable filtering out bad influence from outside,like it's a Digimon itself. He also pulled back tree barrier from Geko Swamp since problems there are resolved. As for his card,he promised he'll give you it,only after you collect all other Seven cards.

You return to Factory and Etemon manages to make 100 rolls of toilet paper from it(200 is to much). So you go to KingSukamon,who refuses to give you Sevens Card,and promises to rise Sukamon to new heights. Angered to bones,naturally you fight him and get Reverse Sevens card from him,your toilet paper back,and a promise Sukamon will stop wrecking toilets on island. Then you go to Panjyamon to give him the returned paper,but he's not around. So you go to Drill Tunnel's toilet in underground lake,but there is no toilet paper. Did KingSukamon break his promise? You then return to Panjyamon's Woods area,and he's back. Relieved,seems like went to that toilet,and took some toilet paper from it,which he tries to hide it. He thanks you for bringing him toilet paper and fights you for his Wild Sevens card. Now with six cards,you return to Jyureimon who gives you final,Misty Sevens card,and wishes you good luck in saving the world.

This is it. All Sevens cards are finally assembled,and you return to File City,where Babamon awaits.She decides to go with you on Mt. Infinity, to deal with effects of Bug card once and for all. Betamon also wants to go there,which Babamon dissaproves because of danger,but you are glad to have him on your side. And so,you go to mountain,whose entrance is in back of File City. In the entrance,you meet guardian Airdramon,who doesn't want to fight you,but lets you in and wishes you all the luck in your brave endevaour,and warns about strong Digimon under effect of Bug, which await you. In 1F you encounter WaruSeadramon who guards the floor,and won't let you without a fight. After winning a fight WaruSeadramon reluctantly let you through to 2F. Betamon is tired and decides to slow down,letting you and Babamon forward. On the 2F, guardian Gigadramon awaits. His mind is heavily damaged by Bug card, and attack immideatly when he recognises you as Legendary Hero. After winning,he falls down in critical contition. Babamon remains on 2F,because the system to fix the effect of Bug card is on this floor,and to help Gigadramon and other Digimon. The only thing left to do for you,Legendary Hero, is go top floor,and defeat Mugendramon,to destroy Bug card once and for all.

When you arrive at top floor of mountain,you see Mugendramon who awakens. You confront him for supposed evil-doings,but he denies being involved in it. He's not even familiar with Bug card. Not being able to talk it out, you are in for one final battle. Which you,of course manage to win. But Mugendramon still denies accusations,even pointing out that Bug was not part of his deck.(I'm not sure that's ultimate proof,but okay...) Then,a mysterious flowerhead-woman (Vamdemon's darling) Digimon reappears. Her name is revealed to be Rosemon. She is also revealed to be Babamon's true form. She forces Mugendramon to confess,and give away Bug card. She said she destroyed the power reactor of the Mt. Infinity,and whole mountain will blow up soon. But he still is quiet on matter. Then,Betamon manages to catch up to them. He then sees a card on a floor that he recognises as the one wind blew away from him in Ancient Dino Region. You take a look. It's a Bug card. Everybody is in a state of shock. It was Betamon,who picked a card,lost it in a storm,and card was blown to main system area of the Island. Betamon starts crying because of feeling guilty. You try to calm him down, but there is no time for emotion processing,as reactor starts exploding ,and with it,the Mugendramon's home. They all run away from massive explosion, but somehow manage to escape. They are back in the File City. Rosemon is mad at Betamon at first,but still forgives him. She then quickly deletes Bug card from existence. Rosemon then explains than when Bug card appeared,it corrupted her body(matrix) and she was forced to assume a form of Babamon,form which uses less data. She calls the process 'Exchange of souls',and didn't want to tell anyone about it is because of her 'lady pride'. Mugendramon's home is destroyed,but Rosemon gladly lets him stay in a city,where he works in Card shop,under watchful eye of Tanemon. Since your mission as Legendary Hero is now finished,Rosemon gives you a Downloader card (Download Digivolve) which you can use return back to your own world,and return whenever you want. You bid a tearful farewell to Betamon and Rosemon,promising to return,and become the ultimate Card Master.

And that's it. You return to File Island later,where you can fight Rosemon,Mugendramon,and other Digimon who may appear to challenge you. You can also get Insect Flute from Mojyamon,and play it at Dragon's Eye Lake,which will cause Seadramon to fight you,because it is annoyed by flute. Later,when you're friends,it will take you to Beetle Land,where you can fight in a Bug Card Tournament,where you fight Kabuterimon,or Kuwagamon,and in finals,you fight HerculesKabuterimon.

You can also use TonosamaGekomon's treasure pot,to summon strong cards by passwords (Like Wizardmon in Arena) Also,Fugamon gets tired of Etemon's attitude,and opens Casino in Gear Savannah. Also,ToyAgumon from Toy Town unlocks shortcut to Freezeland,and says Angemon obtained rare 'pakkun' card. It turns out Angemon paid huge amount of money for a fake Bug card Brachiomon lost.
Also,Vamdemon from this game,is the same as one Digital Card Arena,which searches for his darling,as well as his subordinates. Also Picollomon from this game(chance encounter) is appereantly the same as one from Arena,where he says he meets you again,and says 'Little Boy'. And many more funny surprises.
I believe i got it right.