Love-Letter of Flowers

From Biblo Eros:
Love Letter of Flowers: Someone has been giving the new music teacher origami flowers, and he's not quite sure who or why. But a single student comes to mind whenever he thinks about it.

Anata no Toriko (Your Prisoner): Sasaki catches Mikami, one of his students, going through his things one day and accuses him of trying to steal test questions. He then uses this as a chance to get his hands on Mikami... by blackmailing him into having sex with him.

Kinoshita-kun ga Nigate desu (I Don't Deal Well with Kinoshita-kun): Kinoshita has fallen for his teacher and keeps trying to seduce him, which makes dealing with Kinoshita rather difficult. But no matter what he does, Kinoshita just won't give up.

Ashita mo Toshoshitsu de (Tomorrow Again in the Library) Kigawa spends his time studying in the library to see the senpai that he likes. One day he helps younger student Adachi with his homework... just to get him to shut up. From then on Adachi just won't leave Kigawa alone.

Renai Keiken Netsubouchuu (Craving Experience with Love) Otsukawa has always been very popular... to the point where girls inadvertently dumped him thinking he was too good for them. Because of this, he's still a virgin at age 28 and embarrassed to go out with anyone for fear of showing his lack of experience. So, when Koumoto, a male coworker, confesses his love, he decides to use Koumoto to get the experience that he lacks.