Damn, I honestly expected little sis to just kind of silently implode until a shitstorm surfaced, but no, she's going on the offensive. Usually I can't stand stories where everyone but one couple just kinda silently hurts and everything falls apart, but if she's making plays like this, my interest is a bit more piqued.
Really do feel kinda bad for her though, the same connection she feels with her sister, is the same thing her sister apparently hates about her present situation. Since neither of them are going to actually talk it out, now we're in this mess.
I hope Komachi goes for the gold and implicates the teacher when she no doubt turns her down the first time. "But my sister's good enough to make out with, huh?" Then again, teach is kind of dangling on the bad girl line right now, I half expect she'll actually go for it after some prodding.