Mutsumi Kuonji is the main character of Final Examination Kujira Progressive. He is a teenage boy with short brown hair and green eyes, and he is often called Mucchan by those close to him. His backstory is defined by a childhood meeting with a girl named Sae Nagumo, whom he calls Sacchan. The two spent time together and made a promise to meet again at a specific location. Mutsumi, however, never arrived at that meeting place in the past. Years later, while walking to school, he passes through the same spot and discovers that Sae has been waiting for him there faithfully throughout the intervening years. This unexpected reunion leads them to resume their playful interactions, but their rekindled bond carries the weight of the lost time and is threatened by impending circumstances that give their renewed connection a fragile, temporary feeling.

Mutsumi’s personality is not extensively elaborated, but his actions reveal a character who, as a child, was unable or unwilling to keep an important promise, possibly due to the natural forgetfulness of youth or other unstated reasons. As an older teenager, he appears to be someone who is surprised and moved by Sae’s unwavering loyalty. His motivations center on reconnecting with Sacchan and rediscovering the intimacy they once shared. The story largely follows his perspective as he grapples with the consequences of his broken promise and the bittersweet nature of their second chance.

In terms of development, Mutsumi moves from being an absent figure in Sae’s life to someone who re-enters her world and briefly reclaims the joy of their childhood games. The narrative does not equip him with any supernatural abilities or special skills; his journey is purely emotional and relational. His key relationship is with Sae Nagumo, whose patience and devotion define the central conflict. Mieko Satosaki appears as a supporting character who interacts with the pair. Mutsumi’s role in the story is to be the catalyst for a story about missed opportunities, enduring affection, and the fleeting nature of reunion. The OVA leaves the outcome of their time together unresolved, emphasizing the impermanence of the moment they share.