Reborn Analysis Fern the hero that was(not)
Fern is an interesting jerk-rival. He embodies the archetype to a T, right down to choosing to side with the evil team because he is so dedicated to being on the winning side. Fern was also, in the previous timeline, the young hero who got the closest to Lin. I'll try my best to contend with these two realities.
Gameplay and story-wise, Fern has always been hinted to be built from stronger stuff. His Decidueye creates the natural rival dynamic with Cain and Victoria. Victoria's Zen selfishness contrasts with his ego-driven nature, and Fern's directness contrasts with Cain's conflict avoidance. Further cementing this is that, amongst your rivals, he gets the furthest to you in terms of power. His frustrations with you always being ahead of him are a subtle nod to overall you having several advantages he simply doesn't. Two reality shifters are pushing you to shift while Fern only has himself to win. This was never a fair game to Fern.
Yet circumstances further display that, however valid that pain is, Fern isn't actually equipped as a person to handle the task of healing Reborn. The prior timeline suggests he made it and failed at Lin's doorstep. I'll dive deeper as to why in Lin's analysis. What I can say is that Fern, as a person, wants to be the hero, and can be heroic. The end point of his umbral mission shows this, and Florinia's recount of her birthday emphasises that beneath his bluster, Fern wants to be that person naturally.
There are two major reasons as to why he struggles in this space of frustration. One is out of his control entirely, and the other is a deep-rooted one. The former is the easiest to understand. Lin is a god who can only realistically lose when she feels like it. This doesn't make her unbeatable, as the Anna route shows, but Fern could never win against someone who could restart any fight against him and choose the exact team needed to beat him. Lin, or you. He is against an impossible hurdle; he does try his best, though,
Which leads to the second issue that likely was in Fern's control. He struggles to make connections means that he couldn't band the team together to make the final push against Lin. Rescuing Lin requires the player character to motivate the entire cast to assist. Our ability to win is of less importance than our ability to walk with the rest of the cast through their problems. Beating Lin in a game only has her flip the board and demand the rules be changed in her favour. Fern would likely prioritise winning over healing.
I'll use Florinia's memory of her brother as a key example. She tells the story of someone who would neglect getting his sister a gift, but on the other hand fight tooth and nail to get back at her bullies. A strong sense of Justice, even if still egocentric, is deep in Fern's heart. As well as several deep-seated insecurities born from being in his sister's shadow. That internal conflict could not be resolved if Fern didn't have an obstacle to force him to self-reflect, and that obstacle is the player character.
Fern's two major post-game stories revolve around Mew and Mewtwo. The first highlights how he has changed. Fern is now less focused on beating you and more on a healthy competition between the two of you. The childish play area highlights this. He sticks to his word about the winner of the battle getting first dibs on Mew and honestly does his best to find Mew. There are moments when the frustrations get to him, but that is a work in progress. Your rivalry with Fern allows him to focus less on the goal and more on the journey, in that he becomes more likeable.
The other half is him being forced to confront himself. Mewtwo acts as a metaphor for Fern's own quest for power. Metatextually, an imposing Mon, and the definitive legendary Pokemon to many a Pokemon fan. Like you, Fern has to overcome a stronger version of his team. That version reflects back who he has been to people, and it causes him to reevaluate hard. Self-reflection is core to Fern's development, and what is a clone if not another kind of mirror?
The final step in that growth is that he sacrifices for you. Fern went from aiming for cheap shots to take you down in Victory Road to saving you from Mewtwo’s own cheap attack. Frozen in stone and resurrected by the graces of a god, he is forced to spit out his deepest thoughts. An interesting note about Umbral Fern is that he doesn’t have Decidueye. Beyond the balanced reasons of Serperior being superior for a hyper-offence team like Umbral Fern and working better for the Holy field, I want to suggest there's more to this decision.
Signature Pokemon are ways to speak to a character. Serperior was his ace in the prior version, and I'd wager his ace in the previous timeline. It reflects his desire to dominate battles, while its grass typing connects him to his roots. Decidueye then is the result of a new timeline for Fern. The ghost typing represents the various shadows Fern is under. His sister, you and his own ambitions. When stripped away, we fight the kind of trainer he could be, and in another timeline we understand it allows him to grow to be an Elite 4 and most impressively befriend Titania.
Fern's story, when taken as a whole, is that he is the core rival. He is the hero of another story, it just unfortunate the story we experience, he isn't at the centre. To make peace with your limitations, but never allow that to be an excuse for complacency. Fern isn't the type to remember birthdays or speak true to his feelings. He will stand up for you. He will be blunt about his thoughts, and if his job is to heal you before the final battle, he will damn well do his best.