"Hiro, marry me." From the far reaches of Mars, astronaut Kyoya Segawa broadcasts a public marriage proposal to his step-sister, Hirono!

While the world goes wild over these weekly video letters broadcast across the globe, Hirono only grows more exasperated as the spotlight on her intensifies.

Yet when Kyoya goes missing in a storm during his mission, the heart of the girl left behind on Earth finally begins to stir...

An ultra-long-distance love story sending devotion from a hundred million kilometers away.