(referred to as OniSuki for short) is a Japanese seinen manga series written and illustrated by Kouichi Kusano which was serialized on Futabasha's Web Comic High!

After Nao learns the fact, she wants to fall in love normally with Shūsuke because siblings by adoption can marry under the family law in Japan.

However, she finds herself competing with Shūsuke's childhood friend, Iroha Tsuchiura, and his class president and yaoi lover, Mayuka Kondō.

The original manga, written and illustrated by Kouichi Kusano, began serialization on Futabasha's Web Comic High!

DVD comprising all twelve episodes of the anime also includes a bonus CD containing the opening and ending theme songs, and their off vocal versions.

has been adapted by Zexcs into a 12-episode anime television series, which aired in Japan on Chiba TV network between January 9, 2011, and March 27, 2011.