Ciguatera

One day, Naho Takamiya receives a letter written to herself from ten years in the future. As Naho reads on, the letter recites the exact events of the day, including the transfer of a new student into her class named Kakeru Naruse. The Naho from ten years later repeatedly states that she has many regrets, and she wants to fix these by making sure the Naho from the past can make the right decisions—especially regarding Kakeru. What's more shocking is that she discovers that ten years later, Kakeru will no longer be with them. Future Naho asks her to watch over him closely.

Yuu Haruna, a loner and an avid Twitter user, has just transferred to a new school in Tokyo. He ends up befriending a unique high school girl named Fuuka Akitsuki, despite some initial conflict, and the two wind up forming a band together with their classmates. Their relationship becomes strained however when Koyuki Hinashi, Yuu's childhood friend who has become a popular idol, contacts Yuu on Twitter and attempts to rekindle long lost feelings.

Ai, a young girl with shut-in tendencies, who tries not to interact with others. She keeps one of her eyes hidden behind her hair. One day, she happens to stop by a deserted arcade, where she meets "Aka." Spinning the gacha at their urging, she acquires a "Wonder Egg," and from that moment, her fate begins to change...

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.