Sphere-tans

Earth-kun is the faceless protagonist and unreliable narrator.
Londen-tan is a yamato nadesico, the mother figure and president of the Zodiac Outer Classroom's Union.
Minkowski-tan lives in the ceiling space, occasionally removing a panel and dropping down to dispense religious literature. You need to max your zero-g skill to date her.
Daedie-tan is a scowling girl with long red hair and eyepatch, glaring with a single blue eye. She can often be found poking up from behind furniture or out of gratings, stealing cookies and other valuables. Give her sugar cookies and she'll spare you.