It was Wanko to Kurasou played it the whole night and in the morning had to take a test, although I failed my test it was worth it. (Found the game here)
Fate/Stay Night for me.
But the Unlimited Blade Works Patch wasn't available at that time so i needed to wait another 1~2 years until i finally played the whole game xD
its been so long that i cant really remember the order but its one of these
nocturnal illusion, x-change, three sister story or a game of a fake professor who tutored girls and fucked them erotic lesson i things its the name