Kare no Shousou to Koi ni Tsuite

One day, Yajima, who kept on having physical relations only with older partners, met a young man, Watabe. Younger guys were never his type but the hot sex he had with that man made that night unforgettable. What will happen to Yajima, who since then keeps on wanting to have flared up sex with Watabe again...?

(Source: Fujoshi Bitches Scanlations)

Included one-shot:
Volume 1: Kedamono Kareshi!!! (Beast Boyfriend!!!)