"One Punch Man" is moving forward with season 2. The studios have yet to reveal what the plot may be about, but rumors now suggest that Saitama is going to go up against the Hero Hunter known as Garou. This is separate from his upcoming battles against Amai Mask and a rematch against Lord Boros.
Garou had been hinted in season 1 and was shown in the manga as the "Human Monster," a being who has trained so much that he can take down and murder even S-Class heroes. The main draw to Garou, however, is that he has no superpowers. Instead, he simply trained to become powerful, similar to Saitama.
A report from Game N Guide points out that it is possible that Garou will step out of the shadows and start attacking the heroes of the Hero Association. This may force Saitama to get involved and to fight Garou, leading to the climactic battle at the end of season 2.
However, season 2 is also speculated to deviate from the original manga made by manga writer and artist ONE. In the original manga, the Hero Hunter arc involving Garou was quite short. In the remake manga by Yusuke Murata, the story had been expanded and is still ongoing, indicating that the anime may take cues from the remake manga as well.
Garou is not the only enemy that the heroes, including Saitama, will have to face. Lord Boros survived the fight against Saitama in season 1, and it is hinted that the villain is going to try and fight Saitama again. This may take place before Garou steps out as the main villain.
When the studios announced via Twitter that the anime was indeed moving forward with season 2, no official release date was mentioned. It is speculated that season 2 will premiere in early 2017, although the studios have yet to confirm or deny this.
