Masaharu Katsuda is a supporting character in the anime Trickster. He is a teenager, eighteen years old, who attends the same school as Ryo Inoue. He has short, messy brown hair, tanned skin, brown eyes, and a muscular, well-built physique with a chiseled face. Katsuda is a serious and extremely popular student who is highly active in school life. He is a member of the tennis club, the judo club, and the gardening club, showing a wide range of interests and a diligent, athletic nature.

Katsuda is a former member of the Boy Detectives Club. Although he is no longer an active member, he maintains a connection with the group. His motivations are not deeply explored, but he appears to value his studies and extracurricular activities. When Kensuke Hanasaki urgently asks for his help during a dangerous situation involving Kobayashi and Inoue being trapped in underground discharge channels, Katsuda agrees to assist, using his physical abilities to help Hanasaki reach the scene faster. This demonstrates that he remains willing to support his former clubmates in a crisis.

Katsuda’s key relationship within the story is with Kensuke Hanasaki, who approaches him for aid. He also shares a school environment with Ryo Inoue, who is shown observing him practicing tennis. There is no indication of significant personal development over the course of the series; his role is limited to a single critical rescue moment, where he contributes his athleticism and cooperation. His notable abilities are his physical strength, stamina, and skills in sports such as tennis and judo, which make him a capable ally in a physical emergency. He does not possess any supernatural or investigative abilities, and his personality remains that of a dedicated, popular student who is willing to lend a hand when needed.