Fevered Kiss (2002)

Blurb:
On the night of the year-end party, in high spirits and under the influence of the party’s free-flowing alcohol, Satori ends up sleeping with Asou. Since then, every day that Asou comes over, he does nothing beyond kiss Satori over and over, and as much as it perplexes him, Satori is unable to resist his kisses. But one day Satori hears a nasty rumor that Asou has a girlfriend. Satori begins to wonder, “Why does he kiss me so? And why can’t I refuse him?” Asking himself these questions again and again, what will Satori’s answer be?

Includes the back-up story, Hold Me Tighter!

Source: www.anisearch.com/manga/14792