Sava is an anthropomorphic representation of one of Ooshima's cats, modeled after David Bowie. He has several essay manga dedicated to him, and this is the first of two bunko containing them.

(from ebookjapan):
Cats and humans... A one-to-one, equal relationship. It is episodes of interaction with cats. A collection of humorous and heartwarming stories of the author's days with her beloved cat, Sava. Includes the title story and three others. It is full of the joy of living with cats.