Zen Inubashiri is a high school student featured in the series, identified as a zombie. His exact grade level varies between sources, described as either a senior or junior despite his youthful appearance and short 156 cm stature. He wields two ectoplasmic Chinese broad swords as weapons. Personality-wise, Zen exhibits a hot-blooded and confrontational demeanor, frequently arguing with Chika Akatsuki. He assumes a leadership role within a trio.

A significant character aspect involves his unrequited romantic feelings for Michiru Kita, sparked by the Florence Nightingale Effect when she bandaged his head wound during a zombie hunt. This attraction influences his interactions; he often greets Michiru with "Yo meganekko!" His feelings create tension with trio member Toko Touma, who resents Michiru due to Zen's interest.

Zen's story includes periods under antagonist control. Chitose, of the Akashic Record Reform Committee, manipulates him using a "Dart of Destiny," brainwashing him to attack allies. Later, the character Neli controls him, though he eventually breaks free. These events occur across key volumes, involving his disappearance after a multi-faction conflict and subsequent reappearance.

Within his group, Zen parallels Chika Akatsuki as the close-combat specialist. His trio serves as a counterpart to the main protagonist group, reflecting a "Two Guys and a Girl" dynamic where Zen embodies the melee-focused "Red Oni" archetype. His relationships and role remain consistent throughout.