Ano Naya ~Boku ga Mita Koto Nai Oba-san no Yoru no Sugata~

A young boy named Kei spends his summer vacation at his aunt's place. One night, while sneaking out to hunt for a UMA (Unidentified Mysterious Animal), he discovers his aunt in a shed, secretly performing fellatio on a man. Kei watches his aunt and a man having sex in the shed. He reflects on how she enjoys being penetrated, contrasting it with how she reacts when he plays pranks on her. After this incident, Kei stops playing the 'Kancho' (thousand years of death) prank on his aunt.