Gaito Kurouzu, a sixth-grade student at Aibo Academy, discovers the critically injured Black Death Dragon Abygale in the Darkness Dragon World after its battle with Azi Dahaka. Forging a pact, they unite under the shared ambition to become the strongest and pursue the World Buddyfight Championship title. Gaito maintains a consistently cold and antisocial demeanor, actively pushing others away despite their善意, including Gao Mikado and Bal. This behavior stems from social anxiety in crowded settings and a severe fear of cats. Initially engaging in renegade activities, Gaito defeats middle-school card hunters to return stolen cards to younger students, actions often misinterpreted as malicious. His Buddyfighting style mirrors his personality, utilizing Darkness Dragon World decks focused on disrupting opponents through deck destruction and drop zone manipulation. Early strategies center on cards like Death Dragon Sickle and the Impact Monster "Vanishing Death Hole," later evolving to incorporate "Unlimited Death Drain" and the Dragon Force. An obsession with winning fuels his belief in an undefeated "destiny," leading to intense self-punishment after his first loss to Gao Mikado during the WBC Cup. The pursuit of the Dragon Force becomes pivotal to his development. Obtaining it during his 100th match, he initially rejects Abygale for refusing an attack command, causing the Dragon Force to abandon him due to his closed heart. Witnessing Gao Mikado and Tasuku Ryuenji successfully harness it deepens his frustration. A transformative realization that "sadness is born from a weak heart" allows him to reclaim the Dragon Force, prompting sincere apologies to Abygale and a shift toward gratitude for their partnership. This emotional growth enables the Dragon Force to evolve into the "Style of Retaliation," enhancing his abilities in battles like his victory over J Genesis. Gaito's deck undergoes significant thematic shifts. In Triple D, it focuses on punishing opponents through deck destruction. By Season 4 (X), it shifts to a control-oriented strategy centered on the Set Impact "Death Count ~Requiem~," designed to automatically win after the opponent's third turn. Cards like Black Crest Dragon Zillowzest facilitate searching for this Impact, while Earlbow and Redzett provide life gain and protection. Abygale's evolution into an Overturn form augments this by prematurely ending the opponent's turn. As a contingency, Gaito reintegrates cards from his earlier decks when facing threats to Requiem's activation. His relationships reveal underlying compassion beneath a harsh exterior. He frequently assists younger children at Aibo Academy, reflecting a protective instinct. Following Gao's intervention reuniting him with Abygale during a separation, Gaito becomes more cooperative, aiding Gao and his friends against larger threats like Dragon Drei. He participates in a two-on-one Buddyfight against Kyoya Gaen alongside Tasuku Ryuenji, utilizing their evolved Dragon Forces, though defeated by Dragon Drei. This loss motivates joint training with Tasuku to prepare Gao for the rematch against Kyoya. During this training, Gaito confronts the Grim Reaper in a fateful duel, further honing his skills. Gaito's journey concludes with his decision to accompany Gao and others to Los Angeles, signaling his integration into the group and acceptance of collaborative bonds over solitary strength.