Shusuke and Nao are left alone in the house when their parents go on an overnight trip. Nao takes the opportunity to try and seduce Shusuke by wearing a maid's outfit as he tries to prepare dinner. After washing up after a little accident in the kitchen, the two become paranoid when Nao starts hearing strange panting, which turns out to be the AGE Explorers, who invite Shusuke out on an unsuccessful search for porn, which gives him a cold. As Nao tends to it, Iroha and Mayuka pay a visit, which once again turns into a battle for his attention.
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.
