Manga based on the BL game developed by Alice Blue. Each storyline has a different author:

Prologue: Akira Norikazu

Kurosaki x Higuchi: Reno Amagi

Kurosaki x Shimizu: Reibun Ike

Kurosaki x Yamaguchi: Ryou Sakura

Kurosaki x Yoshioka: Wren Tamaquis (Source: M-U)