Shungo meets Mayu, a succubus who cannot suppress her natural power of attraction, and is surprised to discover she will be living in his home -- and sleeping in his bed.

When Mayu inadvertently insults Reika, the stuck-up student council president, Reika attempts to best her in several competitions.

When Hinako tries to forge a friendship with Mayu, Reika tries to manipulate Mayu into leaving, but Shungo bumbles into her schemes.

Mayu and Reika mind the house while Shungo goes out to train and stumble onto a mysterious secret passage full of traps.

Shungo, Mayu and Reika take a trip to an island, where a competitive Reika becomes upset at how much time Shungo and Mayu spend together.

Shungo, Mayu and Reika fight to escape from a team of soldiers and a strange masked woman.