A beautiful woman with black hair and big breasts of unknown age, commonly known as ''Psycho Lesbian Senpai'', is a popular poster on an underground video site. She posts erotic videos with amateur girls every day. When she was having trouble finding a good challenger for the popular project [If you don't cum for 10 minutes, you get 1 million yen], she was approached by a gentle housewife living next door.
''What's wrong? Why are you sighing...'' ''If there's anything I can do, just tell me!''
She thought there was no way she could talk to her about her problems... but she set her sights on the housewife's ''huge breasts'' and invited her to join the project. At first, the housewife, Midori, was constantly being beaten but gradually her own sexual desire was ignited and the situation turned around... Will Lesbian Senpai be able to win?!