Saitama vs. Deep Sea King

Saitama vs. Deep Sea King is the battle between Saitama and the Deep Sea King.

Prelude
Mumen Rider is sent flying by Sea King and is caught by Saitama, who decides to fight.

Battle
Saitama catches the fallen Mumen Rider and congratulates him on a "nice fight", prompting the Deep Sea King to ask about the new "weakling" that had appeared. Saitama notices Genos and asks if he is alright, to which the cyborg replies with "Sensei..." weakly.

Sighing, Saitama claims that he will pound the "seafreak", angering the Deep Sea King who rushes over and punched Saitama in the back of the head. While his head wobbles, Saitama remains unharmed and unfazed, which impresses the DSK, who proceeds to monologue about how he stands atop all life on Earth. Saitama interrupts him, saying that it is raining so "let's do this". Furious, DSK throws a full-power punch at Saitama, but before it can connect Saitama casually punches DSK in the stomach, ripping a hole in his torso and killing him instantly.

Aftermath
Many people thought of Saitama negatively due to the way he tried to falsely take credit as being the only one who took down Deep Sea King, even though it was true. However some people still held in in high graces after this battle, such as Mumen Rider, and the two became close acquaintances if not friends.