One Punch Man Manga Chapter 78

While training, Speed-o’-Sound Sonic is confronted by former ninja comrades Gale Wind and Hellfire Flame, now monsterized, who urge him to join the Monster Association and kill Flashy Flash. Impressed by their speed, Sonic consumes a Monster Cell to gain power but suffers a stomach ache.

Meanwhile, the Hero Association dispatches heroes to handle Marshall Gorilla in W-City. Zombieman intervenes, tracking the monster and witnessing its clash with Armored Gorilla (now allied with humans), who easily defeats it. Zombieman shifts focus to follow Armored Gorilla.

Elsewhere, Bang vows to personally deal with Garou if necessary, while Sonic struggles with the consequences of ingesting the Monster Cell.