One Night Heaven ~Aka to Kuro no Hitobito ni Sasagu Hommage~

High school at Shinjuku, Tokyo, but in imaginary world created by human brain.
Fates of 18 people are intertwined there.
A girl is in love with a boy, but he only plays with her heart. One day illusion of the girl appears at school, and rumors about her suicide start to spread.
At the same time Ryusei creates "Misuzu" and tries to infest people's minds with "Misuzu" through the internet.
Nagase starts to investigate the connection between the illusion girl and "Misuzu"...

[From vndbreview]