The Guys Who Used To Bully Me Stopped A Month Ago. However, I Never Thought That My Sister Was Being Violated As A Substitute for me

Original title: 僕をイジメてたアイツらが1カ月前から僕をイジメなくなった。だけど、姉が僕の身代わりになって犯されていたなんて。

As the title explains, Akari intervenes on behalf of her bullied brother, and she manages to convince them to stop. But now they just want to rape her. Interesting last scene too.