Atsumori Taira is a young nobleman of the enemy Taira clan (Heike) during the Genpei War. He lies severely wounded when discovered by the protagonist Nozomi Kasuga, forging an early connection despite their opposing sides. He bears the celestial title of Ten no Genbu (Heavenly Genbu), marking him as one of the Eight Guardians within the series' cosmology. His character draws inspiration from the historical samurai Taira no Atsumori of the late Heian period.

After the Genpei War, Atsumori appears in the sequel *Unmei no Labyrinth*. He joins efforts to solve a magically constructed labyrinth threatening a parallel world, exploring its depths and battling the supernatural entities found within. He also participates in modern-world social events depicted in the sequel, such as Christmas celebrations in Kamakura, where interpersonal dynamics and character moments unfold.

Within the game mechanics of the *Ultimate* version compilation, Atsumori functions as a playable combat unit. His specific combat role and abilities are unspecified, though he is grouped with characters specializing in diverse styles like ranged attacks or frontline fighting. His presence contributes to the ensemble cast dynamics during both the wartime conflicts of the main story and the supernatural challenges of the sequel.