Fanart of Satotsuki. Source
Sato, 里 = boorish, countryside
Satotsuki has shoulder-length brown hair with a small green hairclip in it. As her eyes are closed, you cannot see what colour they are. Satotsuki wears a long-sleeved green shirt with four light green dots on the front of it. She wears a brown skirt and brown shoes.
Not much is known about Satotsuki's personality. The light nature of Satotsuki's dream world, along with some of the effects she can get (e.g. fairy and present) suggests that she has a more light-hearted personality compared to Kotozuki.
Not much is known about Satotsuki's past other than that she is, in some way, connected to Kotozuki.