Youjoku ~Tenshi-tachi no Ori~

The protagonist has been living alone for a long time.
His mother died of illness when he was a student, and his father soon brought home a new wife, but things didn't work out.
Living alone, separated from his beloved family, Matsuri, was difficult every day.
Only the occasional visits from Matsuri reminded him of their happy family life.
Resentment towards his father, who had destroyed him and his family.
Hatred towards his stepmother, who had barged into his home in her dirty clothes and separated him from Matsuri.
With each passing year, the hatred for them sinks deeper and darker in his heart.

Then one day, he receives a desperate message from Matsuri.
His father has disappeared, leaving behind a debt.
The debt is being collected harshly, and Matsuri, feeling in danger, comes to stay with the protagonist.

An unexpected chance to reunite his family arrived. The protagonist was eagerly awaiting Matsuri's arrival, but she wasn't the only one to show up.

--That's right, his stepmother's daughter, Rin, was also there.

It's great that his beloved Matsuri is coming.
But to think that his stepsister, the one who was partially responsible for separating him and Matsuri, would also come and live with him!
Matsuri and Rin seemed to be as close as real sisters, and he couldn't separate them.
However, just seeing their close relationship made the protagonist feel as if his family bond has been tainted, and he is torn between love and hate.
Eventually, his long-held resentment suddenly exploded, and he brutally abuses Rin.
With nowhere to go, Rin accepts it, but the protagonist, filled with guilt and long-held resentment, treats her coldly.
But there was no way that such a crazy relationship could go unnoticed by Matsuri...

[From Digiket.]