"Hey, you said you wanted an imouto, right?" First year highschool student, Toujo Basara, was suddenly asked by his father and fell into a state of panic. On top of that, the eccentric father told him he will be getting remarried. He then departed overseas after bringing Basara two beautiful step-sisters. But Mio and Maria's true forms are actually the newbie Demon Lord and a succubus!? Basara was almost entered into a master and servant contract with Mio, but a "reversed" contract was formed by mistake, and Basara is now the master!?
Ecchi
Poor Mugi Tadano . . . The sixteen-year-old is heartbroken after his girlfriend moves away. To ease his troubled state, Mugi takes a summer job at his friend Kazuki’s beachside snack bar/hotel on a tropical island. It seems like the perfect plan-until Kazuki sets Mugi up on a date with Yuu, who’s supposed to be, well, a little less than perfect. When Yuu arrives, however, she’s not the monster that either of the boys had imagined. In fact, Yuu is about the cutest person that Mugi has ever seen. But after Mugi accidentally walks in on Yuu in the bath, the girl is steamed.
15 years ago the world discovered magic as well as mythical beings (basically beings from various legends) in another dimension. Humankind learned to summon these dangerous mythical beings and use their power to great effect. Seven countries formed contracts with these "gods" and gained their allegiance as a result. Gods will chose their summoners on their 14th birthday and give them a stigma. Schools have been set up to train summoners and magical swordsman (basically bodyguards that give the summoners time to cast their spell) as a result.
The story begins with Izumi Hayato running to be student body president. But when a beautiful girl swings in promising the liberalization of love while flinging condoms into the audience, he ends up losing to her and becoming the vice president. At the student council meeting, the newly-elected president invites herself over to Izumi's house, where she promptly announces she is to become Izumi's wife thanks to an agreement – facilitated by alcohol – made between their parents when they were only 3.
Takeru Ohyama, a young normal yet perverted minded guy, got accepted and now goes to a school that, unknown to him, was where combat and magic is used. On the first day, he meets again after three years: Haruko Amaya, his childhood friend, Inaho Kushiya, a girl who says she is his fiance, and Kodama Himegami, a blonde who wants to kill him. Finding out that there are many girls there that just do not like him, he is told that everyone there uses a special magic ability while using an item or weapon called a Maken.
Minamoto-kun has a face pretty enough to make people think he's a girl. Because of his face, he was bullied by the girls in middle school who were jealous of his face. He developed a fear of women due to the trauma and he ended up attending a high school for boys. Just as he enters college and makes a promise to himself to overcome the trauma of his past, his father remarries and asks him to move out of the house. His father arranges him to live with his aunt (Minamoto-kun's father's younger sister) for the time being.
Sequel to Immortal Regis. Reading the entirety of the prequel is highly recommended, otherwise, this story from chapter 4 on will spoil it and be confusing.
Staz is the vampire boss of a section of the demon world, but he has little interest in human blood. He is more infatuated with Japanese culture. When he learns that Yanagi Fuyumi, a Japanese teenage girl, accidentally wanders into the demon city, he jumps to the occasion. However, while Staz deals with an intruder on his turf, the oblivious Fuyumi is killed by a monster and becomes a wondering ghost. The disappointed Staz vows to her that he will find a way to bring Fuyumi back to life.
Three years ago, the world came to know of the existence of humanoid beast creatures after the government decided to stop hiding their existence from the world. It was decided that they would be integrated into human society, and thus the "Cultural Exchange Between Species Bill" was created. Since then, the cultural exchange program became a huge success helping many species integrate into human society.
In the future, people with ESP are becoming more widespread. The Japanese government has hired three of the most powerful espers in Japan to work for B.A.B.E.L. (Base of Backing ESP Laboratory), but all three are ten year old girls with questionable attitudes.