Shūsuke and his friends go on a trip to Akihabara in search of adult goods while Nao and Iroha decide to follow them. After visiting an adult DVD store, the group gets into an argument about their desired fetishes and break off in search of them, leaving Shūsuke alone. However, they soon come to apologize to each other and go to a maid café holding a 'little-sister' service.
Nao Takanashi loves her brother ShÅ«suke despite the incest taboo. Nao thinks that ShÅ«suke is her blood relative, but in fact she is an adopted daughter, whose parents have died. After Nao learns the fact, she wants to fall in love normally with ShÅ«suke because siblings by adoption can marry under the family law in Japan. However, she finds herself competing with ShÅ«suke's childhood friend, Iroha Tsuchiura, and his class president and yaoi lover, Mayuka KondÅ.
