From the day his parents named him, Nasa Yuzaki has felt connected to outer space...whether he likes it or not. His efforts to outperform the space program veer off course when an accident introduces him to Tsukasa, a mysterious girl with strange powers. Is she an alien, a moon goddess, or something else? Since she insists on marrying him, Nasa will have plenty of chances to find out!

In the mountains, Tsukasa and Nasa find a final gift--and a final puzzle--left for them by Tokiko. Can Nasa unlock the high-tech secrets hidden in an antique clock? Or will Tsukasa manage to break things beyond repair? It's high time the couple finally has a talk with Kaguya, the girl genius who acts like she's new to this planet. Not that she'll do anything but drive Tsukasa up the wall.