Umao, a boy who couldn't decide on a theme for his summer vacation free research project, one day saw the mature and prominent figure of 'Rena-sensei,' a talented woman running a private cram school nearby, and had an inspiration. To counter his friend Miyashita-kun raising rhinoceros beetles, he decided to raise this 'neighborhood auntie.' Umao, an innocent and unrestrained boy with an adult-defying massive penis, chronicles through his summer vacation picture diary the shocking SM training erotic drama with Rena-sensei.
