Off the southern edge of Japan lies the Southern Cross Island; in the evening, Wako Agemaki, a resident of the island, finds a boy named Takuto Tsunashi washed up on the shore.

The day after Takuto comes across the Kiraboshi Order of the Cross, Sugata invites him to Night Flight, a production by the high school's Drama Club.

Short on funds, Takuto accepts a part-time job on the luxury liner owned by Kanako Watanabe, a high school student married to a world-famous millionaire.

Wako awakens to discover that she's all alone; she makes her way to the beach, where she finds Takuto, the only other person in this world.

A mysterious young girl named Hina shows up at Southern Cross Academy, a mysterious fragrance constantly emanating from her body; the members of Night Flight discover the link between Hina's true identity and a series of recent earthquakes.

Takuto's pocket watch is broken, so Wako takes him into the city, inviting Sugata along as well; but Sugata isn't his usual self, it's his birthday.