Bond(z) (2003)

Blurb:
It’s not unheard of to sleep with a friend after having too much to drink. But when that friend happens to be a guy, and you both happen to have girlfriends, things can get messy. In a drunken moment of youth gone wild, Tomo and Keita crossed the line from friends to lovers, and there’s no going back. Neither expected such fiery obsession to ignite after a single night together—nor did they imagine how their desire would escalate with each subsequent encounter. Keeping their relationship a secret only serves to heighten Tomo and Keita’s excitement as they embark on a journey to find the limits of human passion.

Source: www.anisearch.com/manga/3420