Hmmm, would you be of the same opinion if Hotaru was a guy? Maybe it just doesn't feel like NTR to you because it's two girls?
The thing with that is that the story fundamentally doesn't work if Hotaru is a guy. What makes the story good(in my opinion) is the queer exploration. Hotaru knows she's in love with Yuma, but she herself sees the relationship as invalid and with no future because of the homophobic attitudes in japan, especially a decade ago. I think she genuinely believes she's helping Yuma, but her ulterior motives are clouding what she's doing. She stays in an abusive relationship with a girlfriend beater just to help Yuma and Takeda's relationship.
I find Yuma and Takeda's relationship the most touching. Yuma
wanted to love Takeda, but couldn't because she's gay and just didn't know. It's really common for queer people growing up in unaccepting environments. You can she tries to follow the steps of the relationship and is happy she's able to perform heterosexuality, but ultimately Hotaru is the only one she's actually able to love. Seeing them growing to trust each other as friends after their breakup was one of my favourite parts of this manga.
The story is just as much about Hotaru realising it's okay to be gay as much as it is for Yuma. Hotaru did
a lot of awful shit through this manga, but just I cannot see it as done out of malice. She does what she does because of the trauma from being abandoned by literally everyone in her life. She just assumes Yuma will be same after she gets other friends and a boyfriend. It's hinted at from the first volume. Obviously all of this would've been much more stable and healthy if they just talked it out, but you can say that about any story.
