Dont Call It Mystery Omnibus vol 4 back

When Totonou's favourite professor asks him for a favor, the usually introverted Totonou can't help but say yes. Professor Amatatsu is planning a weekend getaway in the snowy countryside. Once all the guests are assembled, one of them suggests they play a murder mystery game. But as the snow continues to fall and people start to act more and more strangely, Totonou starts to suspect that this isn't a game at all! Afterward, Totonou gets to spend more time with his friend Leica, a girl he met in the hospital. But there is more to Leica than meets the eye, and Totonou has to deal with a stunning realization about his friend.