National Superhero Registry Arc

The National Superhero Registry Arc is the 4th arc of the series, and the first arc of the Hero Association Saga.

Plot
At the National Superhero Registry exam, Saitama is passing the physical exams without any trouble, amazing the other contestants by his immeasurable speed, endurance and arm and leg strength, breaking every superhero record in the process. In the locker room, Saitama meets up with Genos. They agree that the tests were a walk in the park and Genos adds that the written test was especially easy and thus the fitness test would be the deciding one. One hour later, they get their results, with Genos scoring perfectly everything, 100 points, and being ranked an S-Class Superhero. Saitama however, only got 71 points, ranking as a C-Class. He aced the fitness test, but barely managed to pass the written test. They are then both summoned to a seminar for the passing candidates.

At the meeting hall, they are greeted by Sneck, who congratulates them and gives them a lecture as to what being a superhero is all about. He is irritated by Saitama's nonchalance and yells that they should learn from him to become fine superheroes. Still annoyed by Saitama's dull look, Sneck implies that he can make sure that Saitama loses his rank. Saitama, as always, is completely and utterly uninterested. On their way home, Genos seems happy about them attaining a superhero rank, figuring that this makes him Saitama's official disciple. Saitama is worried about this and regrets making Genos his disciple.

Back at the office of the Hero Association, Sneck complains about the two new superheroes to a fellow colleague. He says that they will probably both quit their jobs soon, but his partner disagrees, saying that Genos is already S-Class, above Sneck, and that both recruits got full points on the fitness test. He further presses that Saitama broke every fitness record and that he may surpass Sneck in no time. Meanwhile, walking on the riverside, Saitama is thinking about the Superhero ranks and revises his opinion about Genos, reasoning that he may actually be pretty impressive. However, he thinks to himself that Genos is not the kind of superhero Saitama wants to be. Suddenly, he is cut off by Sneck, who takes a fighting stance in front of him. He declares that he will fight Saitama because he is a promising newbie, a thing common in the industry. He initiates his hand-to-hand combat technique and connects with Saitama's face, though after a brief off-screen conflict, Sneck's torso is seen buried in the ground, with his legs sticking out and Saitama walking away.

Genos is checking his and Saitama's new rankings in the Hero Registry, claiming that they'd been both put in the lowest rank of the S-Class (Genos) and C-Class (Saitama). After a brief discussion, it turns out that the two have gone to a quarry to spar. Genos asks Saitama to take the spar seriously and then takes a stance.

He holds out an arm, which opens up to reveal multiple cannons, which surprises Saitama. Genos fires a massive beam towards Saitama and then launches himself after the beam. Saitama easily sidesteps the beam but gets caught by Genos which causes the two of them to go flying into the wall of the quarry, shortly followed by the beam. Genos then moves along the side of the wall of the quarry, throwing a flurry of punches until he notices that Saitama isn't there and he'd just been attacking Saitama's after image the entire time.

After realizing that he hadn't actually been attacking Saitama, Genos scans for him and locates him jogging away across the floor of the quarry and launches himself after him. Genos lands in front of Saitama and puts his hands together, both of which open up and launch a massive blast. Genos thinks he'd managed to get Saitama, but Saitama pats Genos' shoulder and then pokes him on the cheek. Genos then throws a punch at Saitama, who dodges, and accuses him of not taking the spar seriously. At that point, Saitama gets rather close to Genos, who attempts to kick at him, but Saitama dodges behind Genos and throws a punch, stopping just before Genos' face, and flicking him on the forehead instead. As Saitama walks away, Genos looks behind him to see a massive dust cloud caused by Saitama's punch.

Five days after their debut as pro heroes, Genos asks Saitama if he can live with him. Saitama protests until Genos offers to pay rent and throws a rather large stack of bills onto the table. Afterward, Saitama is relaxing and Genos is taking notes on everything Saitama does in hopes to learn the secret of his power. Saitama starts to think of ways to get Genos out but is interrupted by Genos who tells him that C-Class heroes get expelled from the organization if they have been inactive for more than a week. Saitama had not known this and rushes out of the apartment to find a crime to solve. Saitama rushes all throughout town, but doesn't find anything and gives up. The next day he does the same thing and is freaking out about being expelled when he catches a kunai that was thrown at him by Sonic, who's name he had forgotten.

Speed-o'-Sound Sonic tells Saitama that this time, he shall finally kill him, but before he is able to finish his sentence, Saitama tells him he is busy and cannot fight him at the time. Leaving Saitama irritates Sonic and thus even promotes him to attack Saitama with his sword, which the latter then shatters with his mouth, much to Sonic's surprise. Saitama who was already kind of annoyed by his unsuccessful search for heroic deeds to do, tells Sonic to back off or else he'll punch him. The two are then spotted by a girl who tells someone that one of them is a "suspicious person", that person then reveals himself to be the (C-Class Rank 6) hero Tanktop Tiger. Hearing that he is a hero, Saitama is convinced to he came to stop Sonic, for attacking him out of nowhere. However, Tanktop Tiger reveals his target was Saitama, who was walking around town with a "suspicious" look on his face since the day before. Hearing that he is the one they were talking about, Saitama tells Tanktop Tiger he is a pro-hero like him, Tanktop Tiger then tells him he has never heard of a hero that looks like him, to which Saitama answers that he is a newcomer.

Tanktop Tiger does not care and tells him to go back where he came from, for he is bothering people, which is bad for the heroes' reputation. Tanktop Tiger then prompts Saitama to fight him if he does not leave, Tanktop Tiger is then being recognized for being in the top 10 of even C-Class. Tanktop tiger is then hit with Sonic's Exploding Shuriken and is knocked out, which terrifies the people around, causing them all to run. Saitama worried for the fallen hero, talks to Sonic about his attack, to which he replies that he only put Tanktop Tiger to "sleep" for he got in their way. The civilians terrified of Sonic, are running around and calling for heroes to help them, which causes Sonic to tell Saitama that since he is also a "hero," that he shall create a situation for the latter to fight him. Sonic then goes behind Saitama and in the air, throwing more exploding shurikens, to which the hero prepares but is shocked to learn they were not aimed at him, Sonic was actually using his - Slaughtering Mayhem Formation at the area around, causing havoc. A lot of damage is done, and people seem terrified, Saitama tells Sonic to stop but he does not listen, telling Saitama that if he won't fight him, then he shall continue with his destructive way. Saitama then saves a child from a falling car, by bending a tree over him, annoyed that everyone seems to get in his way, which he as no time for because he needs to find a bad guy to beat down. Saitama then notices Sonic and the havoc he had caused, and hits the latter to the ground, saying that he hopes said act takes care of his weekly quota.