(TMC) Tsukasa feels like a self-insert of a girl whose feeling got hurt by someone rich and handsome (spoilers).
Almost finished with the game, read a bit further about what will happen during the "golden" ending, so wanted to share my opinion.
So, Shutaro. A handsome, popular son of a local rich mogul, who is generally well liked by everyone. Is he secretly a curse bearer? No. Is he a secret bad guy who is seeking immortality by all means available via, say, his dad's money? Also no. His role in the story? Almost nonexistent. The only thing of note he does is that he confesses to Sato, all while being loved by Tsukasa, who is too cowardly to tell him about it.
Speaking of Tsukasa... I don't think she did anything of note (at least I don't remember her doing anything important). But for some reason she is right in the middle of the cover art. Not Sato, not Yuza, not Avi, not Yumeko, but her.
Cut to the end, and Shutaro is mad, screaming, calling everyone peasants, because his dad was murdered and, being a shady businessman, left Shutaro both money and tonnes of debt to criminals. Shutaro is too afraid to deal with criminals, bit doesn't want to not accept inheritance because he isn't used to living like a peasant.
Meanwhile, mousy Tsukasa... ended up being a daughter of even more shady businessman who got killed, whose money she inherited without any shady criminal hooks. And when Shutaro (with a scummy smile, mind you) offers her to get married, she eventually refuses and says that she likes the other guy.
Honestly, this feels like Tsukasa is a self-insert of some woman atop the writing team. A woman who was pining for someone rich and handsome and was refused a relationship with him. A woman who was for 20 years or so concocting a fantasy of her enacting revenge on him, something like "you bastard, oh if I suddenly got tonnes of money and you became broke, you'd come crawling to me and I'd refuse ro help you. Take that, for not feeling how I want you to feel about me!".
Honestly, soured my opinion on the game extremely hard. I'll finish getting all the endings, but while I can see myself returning to 7 Mysteries in a couple of years, can't say the same about Mermaid's Curse, in no small part to this out of nowhere self-insert revenge fantasy.