Kimi Ni Sachi Are!

[From Attractive Fascinante]:
Naruse Sachi left his student ID at Happy Villa. His kouhai, Kunisaki picked it up and wants to return it. But does Kunisaki expect any favor in return? Sachi-chan kawai-ness is making Kunisaki all nervous and excited. Will Sachi accept being pursued by this first love of his life, his kouhai, and a guy on top of that?
Sequel: Naturalist no Kare