OniAi (Japanese: お兄ちゃんだけど愛さえあれば関係ないよねっ, Hepburn: Onii-chan dakedo Ai sae Areba Kankei Nai yo ne!; lit. As Long as There's Love, It Doesn't Matter If He Is My Brother, Right?) is a Japanese light novel series written by Daisuke Suzuki, with illustrations by Gekka Urū. The series is published by Media Factory since December 2010 and ended on January 25, 2019, with a total of 12 volumes released. There are two manga adaptation series, both were serialized in Media Factory's Monthly Comic Alive magazine. It follows two siblings after the passing of their parents who were forced to live with separate families for six years and have finally reunited and started to live together.

An anime television adaptation produced by Silver Link aired in Japan for 12 episodes from October 5 to December 21, 2012. The series is licensed for home video and streaming distribution in North America by Crunchyroll.

After six years of living apart due to the death of their parents, the Himenokōji twins, Akito and Akiko, are finally reunited when Akito desires to live as a member of the family once more. Although things are fine at first, Akiko begins to express her incestuous love for her older brother, who only sees her as his little sister. Things become more complicated for her when more girls move in with the siblings.