Movie
Description
Raised primarily by his older brother Takatora due to their parents' frequent overseas absence, Mitsuzane Kureshima (Micchy) developed a strong dependence on him. Takatora deliberately shielded Mitsuzane from the Helheim conspiracy to protect his future. During his teens, Mitsuzane joined Team Gaim as a dancer and became Kamen Rider Ryugen to defend the team. His initial motivations centered on protecting friends and finding belonging, fueled by unrequited feelings for team leader Mai Takatsukasa.

Learning of Helheim's threat and Yggdrasill Corporation's manipulations triggered Mitsuzane's descent. Feeling betrayed by Takatora's identity as the White Armored Rider, he prioritized his friends' perceived happiness by manipulating events, including staging an Inves attack on his own team to prevent leaks. This triggered Mai's confrontation and rejection, accelerating his isolation. After Takatora was stripped of his position and banished to Helheim, Mitsuzane assumed the identity of Kamen Rider Zangetsu Shin using his brother's Melon Energy Lockseed and Genesis Driver. He blamed Kouta Kazuraba (Kamen Rider Gaim) for his misfortunes and actively sought to destroy the bond between Takatora and Kouta, aligning himself with the Overlords when Project Ark failed.

His villainous actions culminated in a physical and ideological clash with Takatora, who survived. This confrontation traumatized Mitsuzane, resulting in hallucinations of his brother taunting him as a mere shadow, symbolizing his internal guilt and fractured self-identity. His lowest point came when he succumbed to Ryoma Sengoku's manipulation into a suicide mission against Kouta, only to discover Mai had been dissected for the Forbidden Fruit. This caused a complete emotional collapse, compounded by his belief that Kouta and Mai were dead.

Following the Helheim invasion, Mitsuzane began a path to redemption. He reconciled with Takatora, who helped him cope with his trauma, and gradually sought to atone for his past actions. As the last remaining Sengoku Driver user in Zawame City, he temporarily became a heroic figure protecting the city in Kouta's absence. He defended Zawame during crises like Megahex's invasion and fought alongside other Riders, including the returned Kouta and Kaito Kumon (Baron). Despite his efforts, he declined an offer to rejoin Team Gaim due to lingering guilt over his betrayal.

In later years, Mitsuzane graduated and worked with Takatora abroad while occasionally returning as Ryugen to support former allies. He intervened during conflicts involving Neo Baron, providing Zack (Kamen Rider Knuckle) with a new Sengoku Driver and Lockseeds to combat stolen Yggdrasill technology. These actions reflected his ongoing commitment to making amends, though he maintained a self-imposed distance from his past life, acknowledging some actions were irredeemable.

Mitsuzane's psychological struggles stemmed from believing himself an "irredeemable monster" needing to hide his true self. Others, like Mizuchi, saw him as fundamentally unchanged—a "good sweet kid" shaped by difficult circumstances rather than inherent evil. This contrast highlighted his internal conflict between self-perception and external forgiveness, a tension persisting even during his redemption.