Manabu Konishi is a second-year student and the starting center for Kitasumiyoshi High School's basketball team, where he wears jersey number 14. Before high school, he played on the same middle school basketball team as Momoharu and Chiaki Hanazono. This shared history shapes his initial role in the story. Konishi first appears just before a practice game between Kitasumi and Kuzuryu High. His reunion with Momoharu is strained by a past promise that he feels Momoharu broke, an act of dishonesty that creates a significant personal grudge.

Konishi is a principled individual who values honesty and integrity above all else. He is kind and caring with his teammates and gets along well with his peers, but he is also extremely blunt and direct, especially when confronting what he perceives as dishonesty. He plays basketball with the same moral clarity he applies to life, embodying sportsmanship and straightforward competition.

In the story, Konishi acts as an early rival for the Kuzuryu team, serving as a benchmark for a more disciplined and morally grounded program. His personal conflict with Momoharu provides an emotional edge to their matchup and forces the main characters, particularly Momoharu, to confront the consequences of their past actions. His imposing physical presence as a center and his reliable, honest style of play make him a solid and principled opponent who highlights the early struggles of the Kuzuryu basketball club.