Itoshi no Inma wa Banken Wanko ga Dokusen shimasu

Shiki, who gets randomly hit on by the other guys all the time, has only one male friend, an underclassman Atsuya. Since he can talk and joke around with him like normal friends do, Atsuya has taken a special place in his heart. However, after finding out that Atsuya has a crush on someone, Shiki starts to feel a strange thirst and a burning sensation in his body. Gradually losing control over his growing desire, Shiki kisses Atsuya in a daze. What's the truth behind Shiki's behavior...?! The awkward but loyal watchdog and a guy magnet of a boy's tantalizing love affair with younger top!!

(Source: Mobile Media Research)