Daisuke Komori is introduced as a childhood friend of Goro Shigeno and is first seen during the Little League arc. He is a boy of a shy and quiet nature, who is initially a victim of bullying by Ryota Sawamura. His situation changes when Goro intervenes and invites him to join the Mifune Dolphins baseball team, which not only resolves the conflict but also sparks a lifelong friendship and a long-standing catcher-pitcher partnership between the two boys. His father is a former catcher for the Yokohama Marine Stars, which likely influenced his choice of position on the field.

Komori's personality is defined by his intelligence, leadership, and thoughtful approach to baseball, rather than by overwhelming natural talent or physical stature. He is a model catcher who relies on his ability to read the game and his dedicated, careful preparation. This makes him a fierce competitor who shows no mercy on the field, despite being a kind person at heart. His motivations are rooted in a love for the sport, a strong sense of loyalty to his teammates, and a deep-seated desire to win, especially when facing his friend Goro as an opponent.

His role in the story begins as Goro’s primary catcher for the Mifune Dolphins during their elementary school years. He continues in this capacity when Goro returns from Fukuoka to attend Mifune East Middle School. Their time as a battery in middle school ends with an early defeat in the national tournament at the hands of Mayumura, a pitcher from the powerful Kaido Affiliate Middle School. Following this, during high school, the paths of the two friends diverge. While Goro transfers to Seishuu High to build a new team, Komori becomes the catcher for the already-established team at Mifune High. This sets up a rivalry between their schools, and Komori meticulously plans for a match he desperately wants to win against Goro’s team. Although his team puts up a strong fight, they are ultimately defeated. After the game, a simple game of catch initiated by Goro on a footbridge allows Komori to come to terms with the end of his competitive high school baseball career.

Key relationships are central to his character. His bond with Goro is the most significant, evolving from a childhood rescue to a deep friendship marked by rivalry and mutual respect, as seen in the catch session after their high school match. His relationship with Sawamura transforms from bully and victim to that of teammates and fellow friends. Years later, his role shifts as he becomes a coach and mentor. He appears as a volunteer coach for his old team, the Mifune Dolphins, in an OVA. In the sequel series Major 2nd, Komori serves as the manager for the Nijigaoka Beetles Little League team, where he becomes a formidable and intelligent opponent for Goro’s son, Daigo. In this role, he uses his deep understanding of the game to challenge the young Dolphins, demonstrating how his playing career has informed his approach as a coach. After high school, he continues playing baseball at the university level, primarily as a pinch hitter, before moving into coaching.

His development follows a path from a shy, bullied child to a confident and strategic player, and finally to a knowledgeable coach and mentor. He never possesses the overpowering talent of a star like Goro, but his steady growth, work ethic, and baseball intellect allow him to become a respected figure in the sport. His notable abilities lie in his catching and his command of the game. He is portrayed as a smart defensive player who can handle difficult pitches and calls a thoughtful game from behind the plate. His strategic mind and leadership qualities eventually prove to be his greatest assets, making him a natural fit for a coaching role where he can guide and challenge the next generation of players.