Physical Attraction (2004)

Blurb:
I first met the cool and handsome Narusawa in college. Interested, I approached and said to him half-jokingly, "Let me do you next time." ...that very same day, he was the one who ended up doing me! Then, just when I thought I’d talked myself into believing ours was a purely physical relationship, I came to a sudden realization — I was in love with Narusawa! But I’m always the one calling to see him, and never the other way around. The booty-call has been our only connection so how can I tell him, "I love you," now...?! — Kurata

Source: www.anisearch.com/manga/13815