"Let's be lovers when we are grown up",... It was a promise between Mitsuru, a boy next door, and me. One day, Mitsuru transfers to my high school! He has a twin brother, Ryo. But then Ryo kisses me unexpectedly...?!

Mitsuru is gentle and kind, and he's deeply in love with Aoi. Ryo, Mitsuru's twin brother, is stoic and brutish and loves to tease and torment Aoi. The choice should be clear, so why does Aoi find herself so much more attracted to Ryo...?!