Wow, what a hot mess. Well as hot as a 2 year old mess can be. I think all the messed up things that the characters did were supposed to be explained away by the negative impact their upbringing had on them, which may be too generous of a reading. The blackmail can't really be explained by this though lol.
The topic the authour was trying to write about is something that needs to be written with a lot of care, and it frankly wasn't given enough. The story they were trying to write about was the effects discrimination have on minorities and how it harms them; however, when you make those people the aggressors, it can be hard to see it that way. The main character is a cishet male (lol) with a crossdressing hobby, and I guess straight people are suppose to relate to him? If you make the protagonist likeable it doesn't really matter. Anyways, this sets Gin to relate with the struggles of the others as he questions his own gender and sexuality, but the distress caused by his hobby is that he is almost assaulted and a lesbian blackmails him?? Why couldn't it just be some random guy finding out about him by accident? It would have been better for Gin to struggle together with the others, instead of against them; and then coming to accept himself along with them so that the blackmail is meanless to him. (also maybe make Gin trans so you don't have to throw in Sumon being trans at the end giving almost no trans representation, and Gin can befriend Nakamachi at the bar and then they can help each other out)
So that cleans up the main story kinda, but ono where do I start with Seiji. Literally just stop making him a creep. He can still be possessive and jealous, just don't make his gayness a "dark lust" it makes it seem like all gay people are predators. If you still want that idea, use a parent figure that is constantly berating Seiji for being gay, and he can see Gin as the only person that will accept him for who he is and desperately needs him to. Still weird that he wants to be with Gin even he knows about the crossdressing, and I guess that means he never thought Gin could be trans, or just wants Gin to be a man? Let's go with the former.
I feel like the changes I suggested could have made the manga truer to the authour's intent by portraying the characters more sympathetically; however, this was not the story we got. What we got instead was... an attempt at representation with good intentions, but rather terrible characters, and to put it kindly lackluster writing in general. A score out of 10, with 1 being appalling, 10 being a masterpiece, and 5 being average. About a 3, it's really bad, but could have been worse. There was a happy ending and it was fun to laugh at the ridiculousness, but this manga is more likely to do more damage than good. If people outside of the LGBT community read this and were as be wildered by the characters just given a happy ending as I was, they might leave with the idea that gay people are creepy stalkers out to assault people and that lesbians are aggressive manipulators regardless of the afterword and intent of the authour. At least trans people are okay though 🙃