OniAi, short for 'Onii-chan dakedo Ai sae Areba Kankeinai yo ne!', is a romantic comedy anime series centered around brother-sister dynamics. The story follows Akiko Himenokouji and her brother Akito, who are reunited after being separated for several years. Akiko has a strong brother complex, leading to humorous and awkward situations as she tries to win Akito's affection, while other girls also show interest in him. The series explores themes of sibling relationships and love.