Ep 4. The Modern Ninja

In One-Punch Man season 1 episode 4, entitled "The Modern Ninja," we are introduced to a new protagonist by the name of Speed-o'-Sound Sonic. He is a self-proclaimed ninja who thinks he is stronger than anyone else and is looking for a worthy opponent to prove it. Meanwhile, Saitama is busy looking for supermarket sales and decides to stop by a martial arts tournament that is being held in the city.

Both characters end up at the same event, where Speed-o'-Sound Sonic quickly makes his presence known. He manages to dispatch several of the tournament fighters without even breaking a sweat, leaving behind a trail of destruction in his wake. As Saitama observes the chaos, he sees Speed-o'-Sound Sonic as just another cocky villain who needs to be taken down a peg or two.

Sonic challenges Saitama to a fight, but Saitama refuses, insisting that he is just there to watch the tournament. Sonic, however, is not willing to take no for an answer and ultimately finds himself on the receiving end of Saitama's punch. Shockingly, Sonic is not killed by the blow, but instead just ends up losing his clothes.

The fight between the two characters sets off a chain reaction that ends up causing the entire martial arts tournament to collapse in on itself. In the end, Saitama saves the day by taking down the main villain of the episode, the evil Speed-o'-Sound Sonic. However, Saitama is ultimately left questioning whether or not he truly enjoys fighting after it was so easy to take down his opponent.

Overall, "The Modern Ninja" is a thrilling episode that introduces us to a new anti-hero in the form of Speed-o'-Sound Sonic and shows us once again how Saitama's immense power can both be a blessing and a curse. With fantastic animation and engaging fight scenes, this episode is a standout among a season full of great episodes and sets the stage for the rest of the series to come.