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Not exactly an idea for a new bad ending, but a modification in an existing one: Noriko - Revenge path: After learning of Noriko's deal, you decide to pay her back with her own medicine, you make a deal with your tormentors and help them get their hands on her.

One reason i suggest this version is it would implicate the protagonist more in her fate as well as drawing parallels between the siblings. It would also put the protagonist under the thugs' influence, basically the same position Noriko was in.
Another reason is that i think we should be able to be cold towards her and still save her not because we like her now, but because she is family, despite us still not liking her.

Go to your library, find the game, and click download from there, that should take you to a page where you can download the newest version.

Instead of bad endings (you pick wrong ->game over), I would personally prefer "bad branches" where you still get consequences and perhaps even lose characters but the story can still reach a conclusion, even if it's not the best one, despite that.

Unless that's what you ment.

Huh?! Wha- what year is this?

Jokes aside glad to see more from this game!

A scene where she gets mad and starts acting like a delinquent (possibly a side of her past). Then use this as an excuse to persuade her to embrace this side of her having her dye her hair and adopt a more "gyaru" fashion. With the alternative being we complement her ability to change for Asami's sake promting her to embrace a more "housewify" (although perhaps with a dangerous side hidden in it).