One-Punch Man, Vol. 21

The battle between the Hero Association and the Monster Association finally breaks out. Lower-ranked heroes wade into a chaotic melee while the Class-S heroes push deeper underground, clearing out monsters as they go. Among them, Flashy Flash shows off startling swordsmanship against a duo of monstrous ninja.

Volume 21 of One-Punch Man opens the series' largest set-piece battle, splitting its attention across dozens of heroes and monsters at once. The all-out assault is a cover for Child Emperor's quieter mission to rescue a hostage deep in the Monster Association's lair, and, notably, it is the one volume so far where Saitama never appears.