Souhan no Idealism

The protagonist (default name: Sei) was comforting her own heart with casual sex as usual.
But one night she was greeted by a white haired man dressed like a monk, and found herself tossed into a different world.
And the world was an incomprehensible one where people who attack her with the intent to kill would suddenly commit suicide...!?
Violence x Transfer to a different world x Obsession x otome game x more violence = a violent, messy tale of obsessive love!
Can the protagonist survive and safely return to her original world?
Or will she be unable to return? Or maybe, unwilling to?
This is a story where you deliver happiness.

(Although it shares the same setting as "Nail Lain", it is okay if you have not played it.)