A handsome narcissist and ladies' man, Ikezuki Touya, was instantly attracted when he laid eyes on the beautiful face of company cafeteria staff, Fujii Karen, that was hidden underneath a mask.

He invited her for a meal, instead he got a very straightforward reply, "Is that an invitation for sexual intercourse?" What more, she doesn't feel like being in a romantic relationship with anyone. On top of that, he was told that she is looking for a sex friend who can be in a physical-only relationship with her.

To love an unconventional woman, an unusual relationship between sex friends ensues! Because she is different from her usual self during sex, the kissing and pleasuring were quite bold and aggressive. But contrary to Touya who gets hooked quickly, Karen sticks with their relationship as sex friends up to the end. And then, a man who claims to be Karen's fiance appears in front of them!?

An unpredictable, heart fluttering romance between sex friends!!