Maki Katsuragi, a transfer student at Shijo Minami Junior High, is the son of divorced parents Aya Katsuragi and Kenji Kyobate. His childhood trauma stems from his father's physical and emotional abuse while his mother worked, leading to paralyzing fear during encounters with Kenji. Despite a restraining order attempt, Kenji persistently tracks them to steal money and inflict violence. Maki lives with his overworked mother, independently managing all household duties—cooking, grocery shopping, laundry, and chores—while developing exceptional culinary skills peers admire. Financial strain from his father’s thefts initially deters club participation due to equipment costs.

Physically, Maki has a short stature, fair complexion, black hair, and royal blue eyes, with a slender build and pale skin. During soft tennis matches, he wears a sun visor typically associated with female players, drawing ridicule from teammates.

His personality blends bluntness and introspection. Impatient, he prefers running upstairs over waiting for elevators and exhibits strong independence. Initially perceived as cold or mysterious, he speaks with brutal honesty, openly criticizing the soft tennis club’s stagnation to provoke motivation—a deliberate confrontational tactic. He avoids discussing his emotions but displays high observability, deducing social dynamics like "leader-lackey" pairings and designing strategic doubles partnerships that boost performance. His analytical skills extend to creating tailored training regimens veteran players endorse.

Maki hyperfocuses on mathematics and astronomy, frequently rereading an "Astronomical Almanac," contrasting with forgetfulness about mundane details like neighbors’ names. He repeats phrases like "I see" and swirls his hands while thinking, traits some interpret as potential neurodivergent indicators. Despite emotional restraint, he demonstrates empathy by advising teammates on personal struggles, including gender identity and family conflicts.

Recruited by childhood friend Toma Shinjo for the boys’ soft tennis club, Maki negotiates monthly payments and equipment coverage due to financial precarity. Despite no prior experience, his natural athleticism—attributed to endurance from stairs and beetle-hunting—helps him master fundamentals through observation. As a front-court player paired with Toma, he employs strategic mid-match analysis, identifying opponents’ weaknesses and adapting tactics. Key contributions include restructuring the team’s doubles pairs for synergy and securing tournament victories that prevent club disbandment. His development culminates in confronting his father alongside Toma, threatening lethal retaliation if Toma is harmed.

The unresolved ending shows Maki discovering Kenji threatened his mother. He travels to Kenji’s apartment with a concealed knife, declaring intent to end the threat permanently, leaving his fate ambiguous.