Seika Jogakuin Kounin Sao Ojisan -

The story revolves around a middle-aged man who is hired by an elite all-girls school (Seika Jogakuin). Due to a declining birthrate or specific school regulations, the school employs him as an official "sexual processing" partner for the students and staff. The term "Sao Ojisan" is a derogatory yet descriptive term for his role as a utility sex partner.