Ooboshi Akiteru is a high school student living by a simple, logical code. Efficiency counts above all else. Wasting time is a mortal sin to him—especially on illogical social games like "be mean to the person you like." This pragmatism is constantly put to the test by one person: Kohinata Iroha, his friend's younger sister.
Aizawa Yuuichi returns to his hometown after seven years, a snow-covered city in northern Japan. He moves in with his aunt, Minase Akiko, and his cousin, Minase Nayuki. However, Yuuichi's return to his old stomping grounds is not carefree, as the boy remembers almost nothing from his previous visits.
Naoe Riki is a quiet and sensitive high school student suffering from narcolepsy and experiencing trauma after the loss of his parents. At the most difficult moment of his life, Riki was pulled out of despair by four peers: the charismatic Natsume Kyousuke, his shy sister Natsume Rin, the muscle-head Inohara Masato, and the kendo master Miyazawa Kengo. Together, they form a tight-knit group that has become a substitute for a family for Riki.
The school relationship between Sakuramori Akane and Houjou Saito is far from the best. Constant bickering occurs between them, even over the simplest trifles. One day, they both receive messages from their grandparents and unexpectedly meet for a joint dinner.
Kamihate Uryuu had a difficult childhood; he lost his parents at a young age and grew up in an orphanage. Despite these hardships, the boy never gave up and is doing everything he can to get into a prestigious medical school. He moves into a shrine at the invitation of the head priest there. However, when he arrives, the priest is nowhere to be found. Instead, he meets three beautiful sisters with completely different personalities.
Akeuraji Tsukasa decided on figure skating as his passion too late. This forced him to change his perspective, as no serious skating club would accept him at the age of fourteen. He chose to become an ice dancer performing in pairs, achieving some success. However, his love for solo performances never faded. He never could reconcile with the fact that he'd waited so long to decide during his youth. One day, however, he meets a very young, ambitious, and talented girl named Yuitsuka Inori, in whom he sees himself from years ago, standing at a crossroads.
Inomata Taiki attends a school with a specialized sports program because his mother was an extraordinary basketball player. After joining the badminton team in junior high, Taiki has been an active participant in training. He always strives to be the first one in the gymnasium. However, no matter how early he arrives, he always gets there second, right after Kano Chinatsu, a third-year student on whom Taiki has a crush.
Niijima Keisuke meets a woman named Takae at work, and they hit it off immediately. They get married shortly after and lead a happy, love-filled life, soon welcoming their daughter, Mai. Unfortunately, this happiness does not last long, as Takae passes away at a young age. Despite his wife's death, Keisuke maintains a very good relationship with his daughter, but their lives change drastically.
Yokoya Hitoyoshi is a young high school student living alone, as his family is away from home almost constantly. The boy lacks the motivation to keep his place clean and often suffers from loneliness. One day, a beautiful maid appears at his gate and asks to be hired. As they talk, she eventually reveals that she has worked as a professional assassin since she was a child. However, her employer has retired and recommended she go to the Yokoya estate, which supposedly belonged to his distant relatives.
Okumura Masamune becomes the sole member of his high school’s manga club after his senior peers graduate. The boy proclaims his 100% devotion to 2D girls and expresses a complete lack of interest in their 3D (real-world) counterparts. He soon starts to miss the time spent with people who understood his hobby and passion. These reminiscences are interrupted by a knock at the door. When he opens it, he sees an attractive girl who introduces herself as Amano Ririsa and says she wants to join the club.
Kasukabe Hayato returns from Tokyo to his hometown following the death of his grandmother, Sachiko, who raised him. He has inherited the Familia Café Terrace, the café she ran, but has no intention of continuing the family business. Instead, he plans to demolish the building and construct a parking lot.
In the near future, rising sea levels have submerged most of the land and human habitats. Ikaruga Natsuki lost his family and his leg a few years ago. He decides to find his old home in a small seaside town, which is now mostly underwater. All he has left is a small ship and a submarine inherited from his grandmother, a renowned oceanologist. His hope for a normal life is spurred by a somewhat suspicious debt collector, Catherine. Natsuki’s task is to repair the submarine and prepare it for a journey to the ocean floor to retrieve valuable items left behind by his recently deceased grandmother.