To Every You I’ve Loved Before

Old Koyomi finds a note on his IP device about a 10:00 AM meet-up on August 17. His wife Kazune nudges him to attend, and he goes to the Showa-dori intersection where the ghost form of Shiori Satō’s Imaginality waits. After she disappears, Koyomi suspects a shift into a parallel world and begins to grasp what has happened.

Following Shiori’s disappearance, Koyomi concludes that a Parallel Shift has occurred, though his IP device now shows an error and cannot reveal how far he is from his original world. The sense of a fracture between worlds becomes clear as he processes the anomaly. The moment sets the stage for a journey between realities.

In the parallel world, seven-year-old Koyomi chooses to live with his mother Mayumi Takasaki after his parents divorce, creating a different family dynamic from the original world. This new life introduces altered relationships and choices that will echo throughout the story. The change marks the first major divergence between worlds.

After his grandfather dies, seven-year-old Koyomi experiences another Parallel Shift while walking his dog Yuno. He encounters a young Shiori who runs away and ends up at Imaginary Science Research Institute, where his father works, deepening the connection between his two worlds.

Koyomi stays a night in the parallel world and then returns to his original world, waking up back at his mother's house with the sense that two lives have overlapped briefly. The return restores the continuity of his original life, though the memory of the other world lingers.

As a high school student, Kazune Takigawa approaches Koyomi and claims to be his girlfriend in the 85th parallel world, noting that her world is 85 shifts away. This encounter introduces the possibility of interacting partners across many parallel versions of reality. The reveal reframes their relationship across dimensions.

Kazune explains she hasn't felt a parallel shift in her own world despite the IP's 85-shift reading and the two decide to continue their lives independently. The arrangement allows them to coexist in their respective worlds without forcing a seamless romance across dimensions. This separation seeds further miscommunications and discoveries.

Koyomi greets Kazune by her first name, but she ignores him, leading him to suspect the 85th parallel Kazune has returned home. He invites the original Kazune to a karaoke night to learn more about her experiences in that world, but she reveals she pranked him as payback for a speech at the school’s opening ceremony.

After graduation, Koyomi and Kazune enroll in the same university, and Kazune asks Koyomi to be her girlfriend. They begin building a relationship, navigating the complexities of their interwoven parallel lives while planning a future together.

Koyomi and Kazune join the Institute and contribute to improving the reliability of IP devices, enabling smoother cross-world interactions. Their collaboration cements their partnership both personally and professionally as the Parallel Shift phenomenon advances.

Koyomi and Kazune marry and welcome their son Ryō. During a family visit to an exhibition, an attacker wreaks havoc, but Koyomi’s quick actions save Kazune and Ryō from danger. The incident foreshadows the more dangerous consequences of Parallel Shifts.

A forced Optional Shift targets Kazune, moving her into another parallel world. It’s revealed that Koyomi’s Kazune has shifted to a different world and that the Kazune currently in his world is from the 13th parallel, where her son had died. She eventually returns, but the original alignment of their identities is altered by diffusion.

In a parallel world, Old Koyomi from Hidaka’s world initiates an Optional Shift to reach the old Kazune of this world so he can meet Shiori again at the same intersection. Imaginality resides in the old Koyomi’s consciousness as he and Shiori fail to recognize each other, living different lives. He returns home grateful to Kazune for making his life happy.