Makoto Natsume is the male protagonist of the story, a first-year junior high school student living in Chōfu, Tokyo. Initially, his life takes an unexpected turn when a classmate named Aki Hayama confesses to him, claiming that her grandmother once spoke of meeting a boy with his name in the future. Convinced that she has mistaken him for someone else, Makoto is nevertheless drawn into her quest when she shows him a mysterious painting of fireworks, agreeing to help her find the person she is truly looking for.

In terms of personality, Makoto is characterized as a shy and reserved individual who lacks confidence and struggles with social interactions. He is not depicted as outgoing or self-assured, which makes the sudden and inexplicable confession from a classmate like Aki all the more surprising. His motivations are largely driven by a sense of duty and curiosity; despite being bewildered by the situation, he chooses to assist Aki in unraveling the mystery of the painting and the promise it represents. This decision sets him on a path that challenges his quiet nature and forces him to engage with forces beyond his immediate understanding.

Makoto's role in the story is central, as his connection to the painting and the prophecy is the catalyst for the entire plot. Together with Aki, he travels to the Nagaoka Festival Grand Fireworks Show in Niigata Prefecture, one of Japan's three largest fireworks festivals, believing that the event holds the key to the mystery. His relationship with Aki Hayama is the most significant in the narrative. She is portrayed as a popular, beautiful, and talented student who serves as class president, making her his social opposite. Their partnership is a journey of discovery, as they work together to uncover a secret that connects them across time, involving a promise said to span over eighty years. Through this relationship, Makoto is pushed out of his comfort zone, linking his personal growth directly to their shared investigation.

Throughout the story, Makoto experiences significant development as he transitions from a passive, doubtful boy to someone who must make a life-altering decision within a limited time. The mysterious circumstances force him to confront the concepts of fate, memory, and his own agency. While the narrative focuses on his emotional and psychological journey, Makoto does not possess any supernatural or extraordinary abilities. His notable trait is his underlying determination to seek the truth and help Aki, despite his inherent shyness and the seemingly impossible nature of the situation they are investigating.