Katsumi Morikawa appears as a minor character across multiple franchise seasons. Beginning as a first-year at Hitsue Junior High and later attending Hitsue High School with Izaki, he initially presents as boastful and prideful about his physical strength and perceived cardfighting skills. He frequently bullied Aichi Sendou before the series' events. His personality features significant superstition, marked by regular astrology book consultations. He develops an intense obsession with Team Ultra-Rare member Kourin Tatsunagi, often "fanboying" over her appearances and implying his tournament attendance stems more from seeing her than competing. Despite proclaiming expertise, Morikawa ranks among the weakest deck builders, fixating on excessive Grade 3 units like his favorite card, Juggernaut Maximum. This flawed construction causes consistent gameplay failures: botched rides, ineffective card skills, and trigger activation issues. His persistent losses earn him the nickname "Lose-umi" (or "loser" in English dubs), with Morikawa typically blaming luck rather than his deck-building flaws. His storyline ignites when he steals Aichi Sendou's rare Blaster Blade card, betting it against Toshiki Kai. After losing to Aichi in a subsequent fight and experiencing Aichi's forgiveness, Morikawa undergoes a change of heart, transforming their relationship from bully and victim to friends. He frequently accompanies Team Q4 to regional and national competitions as a cheerleader. His role expands in later seasons to include shop tournaments and school matches. When Kourin transfers to Aichi's class at Miyaji Academy, jealousy drives Morikawa to attempt joining by absurdly declaring himself Aichi's "father," an idea Kamui Katsuragi rejects. Despite poor deck construction, Morikawa demonstrates genuine strategic talent using balanced decks. Borrowing a Nova Grappler trial deck in episodes 51-52 yields multiple victories, including one against Aichi. Similarly, using Kai's Kagero deck against Aichi pushes Aichi to near defeat before Morikawa loses. These moments highlight his latent skill when unhindered by his Grade 3 fixation. He persists with this strategy into the "G" series, using a Spike Brothers deck still overloaded with Grade 3 units. He nearly defeats Chrono Shindou through efficient Grade 3 attacks but loses because every card in his hand was Grade 3, preventing guarding. When questioned about his obsession, Morikawa states he simply likes Grade 3 cards, an answer Chrono respects. The manga portrayal shares his core personality and initiating role stealing Blaster Blade but differs: Morikawa belongs to Hitsue Junior High's CF Vanguard Research Club sponsored by Mr. Mark. Crucially, his manga deck avoids Grade 3-centricity, utilizing a functional Spike Brothers deck mixed with Tachikaze units like Savage King. Trivia notes: Morikawa is the first character shown in the anime series. His name "Katsumi" derives from "勝つ" (katsu), meaning "victory," ironically contrasting his losing streak. Fan perception often views him as obnoxious, though he has a minor following appreciating his lethality with constructed decks.