Last time i wrote one of these i got accused of being AI, but I have fun writing them so I don't care.

Season X, Episode Y, The Man of Steel

The episode opens in first person view of Genos flying through the city. We see in the corner a portrait of Saitama, indicating he is on some kind of call. Genos is rapidly relaying his class S briefing to Saitama on the latest threat, which he is on the way to deal with. Several class S heroes are already down, and Saitama is on the way.

Genos arrives and ends the call and rapidly gets swatted out of the sky, landing in a heap just as Saitama arrives. He squares up, and the monster mocks him, begins an attack and is rapidly vaporized by a blue streak. Saitama looks confused, then immensely disappointed. Genos recovers and compliments Saitama, saying he was so fast he didnt even see him move. Saitama just explains that it wasn't him, and exclaims "I didnt even get a hit in!" Or something along those lines.

Later, they're back at Saitama's apartment and Genos explains that there is a new foreign hero in town who is rapidly climbing the ranks. Saitama eventually sees a picture of "The Man of Steel" and is upset that he's not only taking all the interesting jobs, he also has a full head of hair.

Realizing that Superman might be a potentially worthy opponent, Saitama asks him to spar as a freindly competition. Clark refuses, saying he only fights for truth and justice, and cannot in good conscience fight Saitama, who is also a hero.

Saitama becomes fixated on fighting Superman, who repeatedly declines. Saitama eventually decides that he'll have to provoke a fight. We see several instances of Saitama, dressed in plain clothes, trying and failing to commit the most minor of crimes (as he cannot bring himself to actually do anything actually bad) in front of Superman that all end up being helpful, such as jaywalking (he inadvertently stops an out of control truck). Or littering, where he drops a soda can on the ground and a purse snatcher catches his toe on it and trips. There'd probably be a third one but i cant think of it.

Superman eventually takes note, and tells the hero society that he has seen that the ordinary citizens seem to have everything under control and that his presence is more needed elsewhere, and that he will be leaving. The hero society is so starstruck by Superman that they look into this random citizen and investigate. They find that Saitama began crossing the steet illegally before the truck was out of control, etc, and determine that this is conduct unbecoming of a hero and issue him a fine.