Kaito's world shatters when his girlfriend, Rina, is tragically gunned down on the last day of the third week of July. Consumed by grief and a desperate hope, he dedicates his life to completing Rina's theoretical research on time travel, driven by a mysterious symbol of a trumpet-shaped hose and inexplicably appearing notes that aid his progress.
His first journey back in time, to save Rina, ends in horrifying failure, witnessing her death again despite his intervention. Undeterred, a slightly older Kaito tries again, this time working in secret as a janitor to guide his younger self's research, hoping a more refined approach will succeed. This attempt also culminates in Rina's death, with Kaito realizing he might be an unchangeable part of the tragedy.
A third, even older Kaito, worn down by repeated failures, returns with a grim new plan: to kill the gunman before he can act. In a tragic twist of fate and a moment of panicked misidentification, he accidentally becomes the one to cause Rina's demise, fulfilling the horrifying bootstrap paradox – he is the very gunman his younger self then kills in rage.
Just as this seemingly unbreakable, cruel loop threatens to claim him permanently, a much older version of Kaito intervenes, injecting his dying self with advanced medical technology. This "Architect" Kaito, having experienced countless iterations, has begun a project not to erase the past, but to manage its devastating fallout, subtly guiding other versions of himself and preventing their ultimate destruction. He shares his story with a young, inquisitive boy named Kenji, planting the seeds for a new generation to grapple with the complexities of a fixed, yet perhaps subtly alterable, timeline.
"The Third Week of July" is a poignant exploration of grief, obsession, and the crushing weight of inevitability, questioning whether destiny is truly immutable or if, even within a fixed framework, there is still room for human agency to strive for a different, if not perfect, future.