For high school students like Shouichi Kamita, university entrance exams and the future are common concerns. It is also during this time in life that a mysterious emotion that vexes people of all ages may begin to weigh upon one's mind—love. At this point in his teenage years, Shouichi finds three girls he could see himself having a future with: the ever-cheerful Hikari Tsuneki, who teases Shouichi without mercy, but actually has a softer side; the competitive gamer, Tooru Miyamae, who has difficulty communicating with others; and Shouichi's childhood friend, Kyouko Touno, the sometimes immature shoujo manga enthusiast. Seiren follows Shouichi's relationships with these three girls across three separate arcs, as their feelings grow from mutual interest and blossom into something more beautiful.

Yuuya Nomoto was horrified to discover that the vehicle he was driving was being used to kidnap a high school girl, but he's even more shocked when the girl, Hitomi Uzaki, literally tears her kidnappers to pieces instead! Then she forces Yuuya to drive her to an arena where she bets the value of his organs on herself to win in a death match against a half-lion hybrid! Even more astonishing: Hitomi wins! That's because she's a Therianthrope, a genetically engineered fighter created specifically for the underground death matches known as Killing Bites! And now that Yuuya has been pulled into this dark underworld, he has no choice but to continue working for Hitomi. Because who's going to fight against a girl who's part honey badger?

Aya Asagiri is a middle school girl who has problems both at school with bullying and at home from physical abuse by her brother. While browsing online, a website pops up on her computer featuring a creepy looking person. This person appears to take pity on her, and announces that she has granted Asagiri magical powers.