Kissxsis

Kiss×sis (キス×シス, Kisu×Shisu) is a Japanese seinen manga written and illustrated by Bow Ditama. It began serialization in Bessatsu Young Magazine (now Young Magazine) on December 11, 2005 and has since been published into eight volumes by Kodansha. The series was later adapted into two animated series by Feel; a twelve-episode television show aired from April 5 to June 21, 2010 by AT-X, and an ongoing OVA, started December 22, 2008.

Plot
Keita Suminoe is a third-year Japanese middle school student living with his father, stepmother, and older twin stepsisters, Ako and Riko in undisclosed Japan. Since the remarriage of their parents at childhood, the siblings have always been affectionately close and supportive of one another. Picking up at least a decade later, the trio, now pubescent teenagers, see their opposites in a noticeably less platonic fashion; Ako and Riko frequently flirt and lust after Keita while, much to his chagrin, he fights the urge to give into them. The relentless admiration he receives, coupled with the situations and fan service that often ensues, is the primary basis of the series.

Official

 * Official manga website
 * Official OVA website
 * Official TV anime website