Chapter 115 (Online)

"Encounter" (遭遇, Sōgū) is the 115th chapter of the One-Punch Man manga series.

Summary
Puri-Puri Prisoner continues his search for Nyan as he "swims" through the underground walls of the Monster Association base. He ends up in a small chamber filled with torture equipment and notices Garou chained to the wall, seemingly unconscious. Not recognizing Garou as the infamous Hero Hunter, Puri-Puri Prisoner thinks he's simply another human hostage and moves to release him, introducing himself as an S-Class hero. However, just as Puri-Puri recognizes Garou's face from the wanted posters, Garou awakens and breaks the chains before swiftly pummeling the hero. The S-Class hero quickly understands the grave mistake he made by awakening the mysterious prisoner.

Elsewhere, Saitama continues to wander through the Monster Association base as he searches for someone to talk to about all the noise under his apartment. He is ambushed by a Mysterious Being, and swiftly kills it with one punch. Around the next corner, Flashy Flash lies in wait. He gauges Saitama's size and deduces that he must be a monster, so he dashes around the corner and slashes at his target - however, Saitama easily dodges. Flashy Flash is shocked to recognize Saitama as the B-Class hero who once accompanied Genos to an S-Class meeting in the past. Enraged that he dodged his surprise attack, Flash performs his special Flashy Slash move on Saitama, who simply catches the sword in one hand. Unamused, Saitama accuses Flash of being a monster for attacking him, so he quickly clarifies that he's a hero too. Flash explains that they are in the Monster Association's territory, and tells him he should find shelter. Flash also tells him of the existence of the Monster King Orochi, exciting Saitama as he doesn't realize he already killed him earlier. Annoyed by Saitama's persistence to stick around, Flash runs off at high speeds to abandon him but is shocked when the Caped Baldy can easily keep up with him.

Trivia

 * The Garou vs. Puri-Puri Prisoner fight was expanded from its webcomic counterpart.
 * Saitama walks through a section of the Monster Association base that bears a close resemblance to a portion of the Taman Sari Water Castle in Indonesia.