The quiet stability of Sakuta Azusagawa’s life shatters when the true identity of Touko Kirishima, an immensely popular and anonymous internet singer, is revealed to be none other than his girlfriend, the famous actress Mai Sakurajima. This revelation, which Mai herself had not authorized, causes immediate and widespread turmoil, especially as it corresponds perfectly to a strange dream Sakuta had on Christmas night. Soon after, on April 1st, impossible events that were once confined to collective dreams begin to materialize in reality, while social media posts tied to a hashtag that supposedly turns dreams real start vanishing without a trace. As Sakuta struggles to understand this growing disconnect between his perception and the world around him, he receives a desperate message from an alternate version of himself, one from a reality governed by different events. This other Sakuta warns him: Stop Touko Kirishima before the rewriting of reality becomes irreversible.

Set against the familiar backdrop of Fujisawa and Enoshima, the story follows Sakuta in a desperate race against time to find the truth behind the singer known as Touko Kirishima. His search forces him to confront Miori Mitou, a girl who holds a deep and painful connection to the real person behind the stage name. As Sakuta digs deeper, he learns that Miori is not just another person afflicted by the supernatural Puberty Syndrome, but a unique individual acting as a kind of nexus point, with alternate realities converging around her repressed feelings and relationship with the deceased Touko. This crisis also brings Shoko Makinohara back into Sakuta’s life, as she is now the bearer of the heart that once belonged to the original Touko. Sakuta must navigate a series of encounters with his friends and their alternate-reality counterparts, including a dissociated version of his sister Kaede and a second version of his own self. The key to resolving the crisis lies in a palindrome-like song and the need for Miori to finally confront her grief and express her true feelings.

In the climax, Sakuta and Shoko convince Mai to let Miori perform as Touko Kirishima in her place, a performance that helps Miori begin to heal. After untangling the knot of realities, Sakuta rejects the cynical proposals of his alternate self and works to restore the proper flow of time. In the end, he succeeds, leading to an epilogue set two years later. Sakuta is training to become a teacher at his old high school, Mai has deferred a year of college to focus on acting, and all his friends have moved forward with their lives, their bonds intact. The story concludes as Sakuta, having fully grown from his experiences, offers to counsel a new student troubled by the same Puberty Syndrome, showing that while his own battles may be over, his compassion and understanding remain.