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 defeating several monsters on the way. While the other support heroes are being treated for their injuries, Sekingar starts tending to his own wound and calls Sitch to tell the latter that Waganma has been successfully rescued. He then tosses the phone to Genos, who has a short phone conversation with Sitch. Sitch thanks the hero for his work and apologizes for leaving him out of the initial battle plan and starts to ask for a favor. In a flashback, Drive Knight takes Nyan's body away for examination. Nyan, who is revealed to be still alive, mentions someone who can defeat Monster Association executives with one punch, and Genos realizes that Saitama is fighting against the Monster Association. Genos tells Sitch that he has no intention of following any orders from the Hero Association and hangs up.

Genos then entrusts Waganma in Food Battler Futoshi's care and prepares to enter the Monster Association hideout. Sekingar hands Genos Monster Association intel provided by Drive Knight.

Trivia

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