Kirino Kousaka embodies the ideal student with equally entrancing looks. Her grades are near perfect, and to cover her personal expenses, she works as a professional model alongside her best friend Ayase Aragaki, who abhors liars and all things otaku. But what Ayase doesn't know is that Kirino harbors a deep, entrenched secret that will soon be brought to light. At home one day, Kyousuke, Kirino's perfectly average brother, stumbles upon an erotic game that belongs to none other than his seemingly flawless little sister. With her reputation at stake, Kirino places a gag order on her sibling while simultaneously introducing him to the world of eroge and anime. Through Kirino, Kyousuke encounters the gothic lolita Ruri Gokou and the bespectacled otaku Saori Makishima, thus jump-starting an entirely new lifestyle. But as he becomes more and more involved in his little sister's secret life, it becomes that much harder to keep under wraps.

After the accident in which she lost her mother, 16-year-old Tooru moves in with her grandfather, but due to his home being renovated, is unable to continue living with him. Claiming she will find someone to stay with but also fearing the criticism of her family and not wanting to burden any of her friends, Tooru resorts to secretly living on her own in a tent in the woods. One night on her way back from work, she finds her tent buried underneath a landslide. Yuki Souma, the prince of her school, and his cousin Shigure Souma, a famous author, stumble across Tooru's situation and invite her to stay with them until her grandfather's home renovations are complete. Upon arriving at the Souma house, Tooru discovers their secret: if a Souma is hugged by someone of the opposite gender, they temporarily transform into one of the animals of the zodiac! However, this strange phenomenon is no laughing matter; rather, it is a terrible curse that holds a dark history. As she continues her journey, meeting more members of the zodiac family, will Tooru's kindhearted yet resilient nature be enough to prepare her for what lies behind the Souma household's doors?

Every morning, incoming first-year Taiki Inomata hurries to his high school gym in order to further refine his badminton skills. However, his true motivation stems from sharing the otherwise empty gym with second-year Chinatsu Kano, Taiki's crush and the star player of the girls' basketball team. Although Chinatsu seems unapproachable, Taiki gradually finds opportunities to get to know her little by little. Unbeknownst to Taiki, his tireless work ethic and admiration motivate Chinatsu to work harder and strive to achieve her greatest ambitions. When her family must suddenly move overseas for work, Chinatsu decides to remain in Japan and shoot for victory at the national level. With nowhere to stay, she is taken in by Taiki's mother, who is longtime friends with Chinatsu's own. Overwhelmed with the new reality of living alongside the girl he loves, Taiki resolves to join Chinatsu at the national level in his own sport—and grow closer to her in the process. Still, despite being good enough to catch his coach's eye, Taiki must fight an uphill battle to qualify for a spot on the starting team. Cheered on by both Chinatsu and gymnast Hina Chouno, his childhood friend, Taiki aims to make a name for himself among his powerful upperclassmen.

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.