TV-Series
Description
Kouji Ibuki first appeared as a quiet, gentle, and soft-spoken elementary school classmate of Toshiki Kai and Taishi Miwa, often perceived as weak. He found confidence playing Cardfight!! Vanguard, attempting to make friends by letting others win. This strategy backfired, fostering resentment and solidifying a loner personality after peers refused to play with him.

During this time, he introduced Kai and Miwa to Vanguard, teaching them the basics. He possessed the card "Blaster Blade," which he later gave to Kai; this card eventually reached Aichi Sendou, becoming central to Aichi's journey. In the Neon Messiah movie, Kouji resurfaced as the primary antagonist after the Deletors corrupted his memories. Manipulated by Oksizz, he gained the power to "Delete" opponents' Vanguard units, reducing their power to zero and nullifying their abilities. Using a Deletor deck, he defeated fighters including Ren Suzugamori, Aichi Sendou, and Kamui Katsuragi before losing to Aichi and Kai. This defeat freed him from the Deletors' influence but left him traumatized.

Seeking redemption, Kouji traveled the world. He encountered Rive Shindou, who revealed the threat of Ryuzu Myoujin. Rive entrusted him with the Gear Chronicle clan and three "Depend Cards," tasking him with preparing Rive's son, Chrono Shindou, to confront Ryuzu. Kouji later became coach of Team Demise and an employee at FIVA's United Sanctuary Branch, positioning himself to infiltrate the Vanguard Association and monitor Ryuzu.

In the G series, Kouji adopted a colder, more reserved demeanor, though he displayed occasional warmth around colleagues like Mamoru Anjou. He anonymously sent Chrono the Gear Chronicle deck and a map to Card Capital 2, initiating Chrono's journey. As Chrono's mentor, he tested his growth through strategic cardfights, often using his signature Link Joker Messiah deck—a clan focused on locking and unlocking units to gain advantages. This deck symbolized his atonement, contrasting with his earlier Deletor deck.

His covert role culminated in stealing a Depend card and revealing Ryuzu as the true enemy to Chrono after their duel in G Season 2. He organized allies from the original series to combat Ryuzu, participating in missions like the Star Gate Branch G Quest. During Stride Gate, he confronted Ryuzu directly but was defeated. After Ryuzu's defeat, Kouji was promoted within FIVA and continued participating in tournaments, including the Under20 Championships as a sponsor.

In the manga and V series reboot, Kouji attended Fukuhara High School alongside Ren Suzugamori and Asaka Narumi. Here, he wielded PSY Qualia to enhance his cardfighting abilities and reused a Deletor deck. His confrontational demeanor resurfaced, leading to conflicts with Aichi Sendou's friends and duels against fighters like Tetsu Shinjou and Kyou Yahagi.

Outside cardfighting, Kouji demonstrated advanced martial arts skills, incapacitating United Sanctuary employees and rival fighters like Shouma Shinonome, complementing his strategic cardfighting style.

Kouji's decks evolved: starting with Link Joker Deletors focused on Vanguard deletion in Neon Messiah, shifting to Link Joker Messiahs emphasizing unit locking/unlocking in the G Series, and later using upgraded Messiah decks incorporating "Omega Lock" and units like Genesis Dragon, Trans-else Messiah. His battle record includes key victories and losses against opponents like Chrono Shindou, Kamui Katsuragi, and Aichi Sendou.