Supreme Hero Arc

The Supreme Hero Arc is the nineteenth arc of the One-Punch Man series, and the fourth arc of the Neo Heroes Saga.

Plot
Saitama encounters Rangor, one of the nine warriors of the Dragon Alliance, and defeats him with a single punch. He then comes across a group of people calling themselves the Saints. They explain how by defeating Rangor, Saitama has protected the Cruel Dragon seal and saved the world, and then tell the legend of Cruel Dragon: a creature that descended upon Earth, taking countless lives and scorching the land. They explain that ancient warriors managed to weaken the dragon with costly sacrifices, allowing seal masters to seal away the essence of the dragon in nine seal stones, which are now scattered in temples across the land. This brought rise to two groups: the protectors of the seal stones, the Saints, and a group hoping to resurrect the dragon, Deathbone. The two groups have been in conflict for 800 years, but Deathbone recently increased their activity, taking advantage of the recent frequent monster incidents. One of the Saints hold down a member of Deathbone, who begins to monologue as he loses consciousness, until Saitama throws a bucket of water on his face. Saitama eventually resolves that if the dragon will resurrect at some point, it would be smart to resurrect it promptly to defeat it quicker. Much to the Saints' dismay, Saitama picks up the Deathbone member and flees from the Saint members chasing after him, who help him locate all nine seals. After the Deathbone member conducts the ceremony, the Cruel Dragon resurrects, and Saitama defeats it with a single punch.

Saitama picks out groceries.

Later that night, Saitama meets up with Genos on a street leading towards former A-City. Genos is visibly damaged and explains that it is from a battle against a powerful demon level monster when Saitama asks, and requests another spar with Saitama. He then mentions that Dr. Kuseno has shown great interest in Saitama's physical abilities and wishes to collect his data. Saitama asks Genos what he bought and Genos lists the items, adding the fact that he got them for cheap. Saitama is impressed by this and compliments him by telling him that he's mastered the trick to buying stuff, even admitting to missing out on some AAA batteries at half price. Suddenly, the two encounter Sweet Mask who offers to meet up for a cup of tea tomorrow noon as he wants to discuss something in person. Genos refuses the offer, believing that Sweet Mask is talking to him, but it is then revealed that he was speaking to Saitama.

The next day, Saitama and Sweet Mask are sat on a table in a cafe. A waiter approaches them and asks what they would like; Saitama orders a coke and Sweet Mask orders a lemonade, but Sweet Mask orders a ginger ale for Saitama instead of the coke, which irks him.

Later, Sweet Mask has lunch with Saitama and tries to teach him how to be a good hero. Saitama ignores most of what Sweet Mask has to say, so Sweet Mask decides to move somewhere else to continue his talk. They walk to a carnival and sit in a Ferris wheel cabin. Now able to speak in secrecy, Sweet Mask reveals his past to Saitama. He explains that he was born an unsightly human, so he adhered to strict moral principles to compensate for his ugliness. He started working as a hero, but his overwhelming loathing for his looks resulted in a transformation that turned him into a monster with a beautiful face. Sweet Mask then tells Saitama that he is the one person he found worthy of carrying on his legacy and becoming the ideal hero. Saitama turns down the offer and jumps out of the cabin to meet Genos.

Suddenly, a commotion on the fairgrounds catches Sweet Mask's attention. The cause of the ruckus is Pesky Clown, who had killed several guards that had attempted to stop him. The monster swings his mallet to hit a civilian, but Sweet Mask shows up and stops the attack. The two engage in combat. Sweet Mask has the upper hand at the start of the battle and destroys three of the monster's life balloons. However, the monster draws power from the attention of the crowd and transforms, becoming powerful enough to overpower the hero. Sweet Mask then decides to unveil his monster side in order to defeat Pesky Clown.

Sweet Mask then returns from the rubble to engage the monster again. Outside of the fairgrounds, Saitama runs into Genos, who is on his way to the monster sighting to aid Sweet Mask. At the scene of the battle, Sweet Mask has successfully overpowered Pesky Clown using his monster form. The civilians still gathered there now catch sight of Sweet Mask's unsightly face and begin to question if he is actually a monster. Pesky Clown uses the worldwide attention Sweet Mask is recieving to increase his power even more, giving him a gruesome transformation, and the two engage in combat once more. The two fight desperately until Sweet Mask finally dispatches Pesky Clown with a brutal punch.

Now that the people can clearly view Sweet Mask's true appearance, he is berated as people begin to fear him. Blue Fire arrives with the intent to support Sweet Mask in battle only to not be able to recognize him until he is pointed out by a member of the crowd. Like the others, he is fearful of Sweet Mask and classifies him as a monster. Saitama is the next hero to arrive, and catches a rock thrown at Sweet Mask. Instead of berating him like the others, Saitama supports him. Sweet Mask doesn't acknowledge this and wants Saitama to kill him, hoping that Saitama will be seen as a hero for defeating him. Saitama ignores the request and continues supporting Sweet Mask. Sweet Mask attempts to attack Saitama, latching his hand around Saitama's head in order to show his strength. Saitama jumps away, carrying Sweet Mask with him. The news of Sweet Mask's true appearance continues to spread and he becomes more and more disliked by the general public. The news is regarded as the beginning of the Hero Association's collapse.

Later, a Hero Association scouting team makes its way to Suicho's dojo. They are met by Suiko, Suicho's granddaughter and Suiryu's younger sister. She asks the scouting group if she can join the Hero Association as an S-Class hero and comes back with them.

At the Neo Heroes headquarters, several Neo Leaders converse about the situation surrounding Sweet Mask. Webigaza is emotionally impacted by the situation, remarking that she wanted to defeat him herself. McCoy figures that the Hero Association is beginning to fall apart and that the Neo Heroes are officially on the same authoritative level as them. Darkshine and Metal Bat wonder where Blue is, considering he is number one in the Neo Heroes and hasn't shown himself. It is revealed that he left to pursue the case surrounding Sweet Mask.

Story Impact

 * Sweet Mask reveals his past to Saitama.
 * Sweet Mask is revealed as a monster to the public and is forced to retire.