Chapter 120 (Online)

"The Only Necessary Thing Is Strength" (必要なのは強さだけ, Hitsuyō Nano Wa Tsuyosa Dake, Tonari: 162) is the 120th chapter of the One-Punch Man manga series.

Summary
Genos takes the support team and Waganma to an area guarded by the Hero Association. Sekingar hands Genos Monster Association intel provided by Drive Knight. Genos has a short phone conversation with Sitch, who thanks the hero for his work and apologizes for leaving him out of the initial battle plan. In a flashback, Drive Knight takes Nyan's body away for examination. Nyan mentions someone who can defeat Monster Association executives with one punch, and Genos realizes that Saitama is fighting against the Monster Association.

Genos then entrusts Waganma in Food Battler Futoshi's care and prepares to enter the Monster Association hideout.

Trivia

 * Murata wanted to draw a Halloween-themed cover page for the online release but didn't have enough time.