Yuma Isogai features in the spin-off *Koro Sensei Quest!* as part of the hero class dedicated to defeating the Demon King Korosensei. His design translates elements from the original series into a fantasy game setting.

In this adaptation, Isogai dons distinctive blue and white hero armor. However, a persistent glitch prevents any armor or clothing from covering his back, leaving it perpetually exposed, including his underwear. Attempts to conceal this state, such as hiding in shrubbery, cause the obstructing elements to vanish due to the bug. This glitch humorously serves as the in-universe explanation for his partial armor, attributed to his character's financial limitations within the game's logic.

His role as the natural leader and class representative continues. He remains a respected and popular figure among his classmates. During an attempt to enter the Elf Queen's realm, which demands purity of heart and mind, Isogai and most male classmates fail to pass the barrier. This failure ties into his armor glitch, though the barrier's exact criteria remain ambiguous.

The spin-off does not explore his family background or socioeconomic struggles from the main series. Instead, it incorporates his poverty comically through mechanics like the half-armor trope. His core personality traits—approachable leadership, reliability, and modesty—endure. However, the narrative emphasizes exaggerated game mechanics and comedic situations arising from character-specific bugs over deep character development or backstory expansion.