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 second of two bunko containing them.

(from ebookjapan):
This is the second volume in the series describing the author's casual days with her beloved cat, Sava. Includes the title story and five other stories, including "Sava Time," a heartwarming essay manga about enjoying seasonal events with a cat. Life with a cat by your side is wonderful!