High school of the dead fanfics that deliver on the zombie action? That's a surprisingly tough niche to fill well. The best one I've found is actually a crossover called 'Dies Irae: Resurgence,' which merges the HOTD cast with the 'Black Lagoon' universe. The zombie action is relentless because it's set in Roanapur, a city already drowning in violence. When the outbreak hits there, it's less about survival horror and more about a chaotic war zone where every faction—triads, mercenaries, the Church of Violence—is fighting both the undead and each other. The gore is visceral, the pacing never lets up, and the action scenes have a brutal, tactical weight the original anime sometimes lacked. It captures that manga-style over-the-top violence perfectly.
Another solid pick is 'Code of the Dead,' which expands Saeko's backstory into a full-on narrative. It follows her through the initial Tokyo outbreak before she links up with Takashi's group. The action here feels more personal and desperate, focusing on her swordplay against increasingly dense hordes in tight urban spaces. The writing gets the mechanics of zombie combat right—the exhaustion, the splatter, the constant need to move. My only gripe is it can get a bit heavy on internal monologue mid-fight, which occasionally kills the momentum. Still, for pure, unadulterated undead slaughter with a familiar face leading the charge, it's hard to beat.