With his parents abroad and his house in renovation all of a sudden, Kouta Kazama ends up staying at the home of his neighbor, Aki Hayama, sharing a room with her. Being childhood friends, they used to be very close, but now, as a man and woman sleeping together, it might not take too long for them to realize their true feelings for each other.

After living an uneventful life, our protagonist finds himself in a situation he absolutely was not prepared for! Being drained constantly of his seed to appease the lust and hunger of the succubus he now finds himself attached to.

Oyasumi Sex alternates between the views of the siblings Akira and Yui, who have a normal and peaceful relationship with each other. However, when their parents divorce, the young Yui is devastated and clings to her brother all the more, who has decided to take good care of her. As the years pass and Yui gets older and bigger, she starts to develop certain qualities that slowly lead to Akira developing lewd thoughts and making it more and more difficult for him to control his desires. Where there used to be care and love, now there is only carnal yearning.

Aina Endou is a nice, cheerful, open-minded girl, but she can also be very direct. Even if you can’t tell by looking at her, she likes to rebel against the school rules and runs around with dishevelled hair, eats sweets at school that are actually banned, and casually addresses her teachers with nicknames. Amongst them is her homeroom teacher Tanaka, whom she always just calls “Tanakacchi.” Trying to talk some sense into her, he asks her to join him in the classroom after school. Once the two of them are alone, however, she doesn’t hold back and teases him with kinky insinuations, makes a pass at him, and finally claims him all to herself.

Currently, summer will start in my second year of college. My acquaintance introduced a girl to me and then we started dating. I don't think I deserve it. She is beautiful, cheerful, and a little bit spoiled. But the days I spent after ended two months. She was having an affair with a man who turned out to be her boyfriend I know.

After being childhood friends for many years, she sees more in him than just a friend. She wants a more intimate relationship... It just so happens her parents won't be home and she convinces him to come over… Infatuated with a girl at school he asks her to wear something a bit more...lewd next time they meet up. Embarrassed, she shows up and he couldn't be more excited to see and feel every inch of her body!

Souichi Takasaki gained the ability to control other people’s bodies without their permission and decided to use it on the women around him. His sister in law, a classmate and a teacher, all targets of his, he trains to become his personal harem.

Sakurai Taichi, facing a financial crunch, lands a job as an assistant on a film shoot where he reunites with his schoolmate and the most beautiful girl in school, Himawari Kanan. To his surprise, the shoot turns out to be for an adult video, which initially shocks Taichi, who tries to decline the offer. However, Kanan accepts the role, claiming it will be an educational experience. Despite feeling uncomfortable with Kanan’s bold actions, Taichi finds enjoyment in working alongside her. During the shoot, the lead actor has an accident, and Taichi steps in to replace him, which leads Kanan to also participate in the video.

Shouta is very affectionate towards his sisters Rena and Aina, they grew up as close siblings. Day by day, he becomes more affectionate towards Aina… and eventually he even sneaks into her room at night!? Rena tries to stop Shouta, but ends up receiving his affection in Aina’s place. Due to her hidden feelings for Shouta and the pleasure of experiencing things for the first time, the once innocent Rena is steadily being trained by Shouta…!?