Saihate no Diasta  

Diasta of Ultima Thule, 最果てのディアスタ

In the distant future, there's an unexplored region of space known as New Space. The potential for discoveries and dangers in this area is uncertain. Reina and Rio made a pact to venture into New Space together someday. Despite being separated, they were eventually reunited when Rio joined Folshion, a commercial luxury cruise liner spaceship. As a tomboy with no self-consciousness about her gender identity, Rio was welcomed on board the ship provided she found a role for herself. With their bond restored, the sisters began dreaming of the adventures that awaited them in the uncharted territory of New Space.