After living with his grandparents for 10 years, Yuu Shirakawa moves back in with his mother. As it turns out, she has remarried. Her new husband has three beautiful, young daughters who are now going to be Yuu's stepsisters. Due to the nature of his work, Yuu's now-stepfather is often away from home, leaving the house to his children to use as they please. As he settles in his new room, Yuu notices a mysterious package addressed to him. Inside, he finds a glass bottle labeled "Vial of Inanna," which apparently contains a deadly curse he is now afflicted with. The only way to lift the curse is to collect a significant amount of female bodily fluids while leaving their owners unaware of its existence. As horrible and difficult to fulfill as that may sound, Yuu soon realizes that the presence of three more-than-willing-to-cooperate girls in an empty house might be helpful.

Kawakami City is famous for its strong dedication to its samurai ancestors. A healthy fighting spirit is always valued and it's even an important factor for success at school. Yamato, a second year student from Kawakami High school, is always with his close friends (4 boys and 3 girls). They have all known each other since they were young and have done many things together. While they have many other friends, this group of seven is a close-knit, inseparable group. They even have a secret base where they meet. With the new semester, they welcome two girls into their group and shortly after things begin to change...

Shirou Emiya lost his parents in a fire when he was young and was later adopted by the sorcerer Kiritsugu Emiya. Shirou is drawn into the Holy Grail War summons a female "Servant" known as Saber to protect him and obtain the Holy Grail.

The girls of Class 1-C are starting their tenth-grade year with a new teacher: Becky Miyamoto, an 11-year-old MIT grad! She’s an intellectual titan—but can she handle the temperamental teens and idiotic aliens that await her instruction?

In the distant future, mankind is divided into two factions: Union and Deague. They have waged a war against each other for so long that no one remembers when it first began. Sara Werec, the daughter of a respectable family, is a 16-year old girl who attends a Space Academy where she is training to become a pilot. Her brother, Ralph Werec, had been sent to the frontline to accomplish a special mission when she was 11 years old. The two of them had lost their parents when they were young and the bond between the two is very close. It is Sara’s dearest wish to be reunited with her brother. To do that, she must travel to the battlefield where he is. One day, Sara’s planet is suddenly assaulted by Deague forces. To her surprise, her brother, Ralph, turns out to be one of the raiders who successfully kidnap a mysterious girl sleeping in a capsule.

Kasugano Haruka and his sister Sora have lost both their parents in an accident, and with them all their support. They decide to move out of the city to the rural town where they once spent summers with their late grandfather. At first everything seems familiar and peaceful, but changes come as Haruka starts to remember things from his youth.