Kanaami -Osananajimi Ami no Baai-

The childhood friend confessed her love to the protagonist.
Both believe they're fated to be together, but that means something different to him.
Disappointed and trembling, the friend is violated in captivity.
It's not an act of cruelty or revenge in his mind... it's an act of love.
This is how the twisted protagonist knows how to express himself.

[From DLsite English]