Why Do My Innocent Childhood Friend's Lips Taste Like Cigarettes?

Kanna (27), a calm and soothing "older sister" figure, and Mitsuru (21), a straightforward and kind young man, are childhood friends. However, the gentle, reserved, and kind-hearted image Kanna projects is a facade she only maintains around Mitsuru.

One night, Kanna heads to a club to satisfy her desires and unexpectedly runs into Mitsuru. Things take a shocking turn when Mitsuru stumbles upon messages from Kanna's casual hookup partner, sparking jealousy that leads to an impulsive kiss. Kanna is left reeling, not just from the kiss, but from Mitsuru's unexpectedly experienced touch.

As secrets unravel and masks fall away, who's really been deceiving whom? A provocative and thrilling romance ensues as these two navigate their hidden sides in a see-saw game of love and desire.