One-Punch Man Episode 8: The Deep Sea King

A Seafolk messenger emerges from the sea in City J, announcing that the Seafolk will invade the surface to kill all humans. Saitama, returning from shopping, punches the messenger into pieces before heading home.

Mumen Rider receives a call from Hero Association headquarters about the monster threat in J-City and pedals there urgently, arriving to see the messenger's remains and overhear the crowd crediting a bald hero named Saitama. He searches Saitama online, noting divided opinions on his strength despite impressive feats.

At the coast, large Seafolk monsters emerge, led by the Deep Sea King. A-Class hero Stinger battles them with his Bamboo Shoot spear, defeating many but sustaining heavy injuries; he finishes the last four with a Gigantic Drill Stinger Quadruple Thrust, only to be swiftly defeated and hospitalized by the Deep Sea King.

Saitama and Genos watch news of Stinger's fight while Genos dries dishes; they decide to head to J-City, with Genos scouting ahead. Lightning Max arrives and attacks the Deep Sea King but is quickly thrown off a building.

Puri-Puri Prisoner, a Class S hero in a prison jumpsuit, rescues Max mid-fall, then confronts the Deep Sea King to avenge his injured comrades Max and Stinger. He starts at half power, flexing to shred his hand-knitted tank top gift from his boyfriend, enraging him further; he transforms into Angel Mode with wings, landing blows but ultimately getting defeated.

Speed-o'-Sound Sonic races against the Deep Sea King, who pursues him; as rain falls, the Deep Sea King absorbs moisture, shrinking initially on land but growing larger, stronger, and faster into a more hideous true form. Sonic slips away naked after a near-fatal grab, vowing revenge, while warning Genos to back off before fleeing.

Saitama encounters Mumen Rider en route and they search together, but Saitama detours after spotting the naked Sonic. Genos scans the area and heads to the evacuation shelter where civilians have gathered amid pouring rain.

At the shelter, Class C hero Allback Man steps forward to surrender on behalf of the civilians, buying time for stronger heroes, but the Deep Sea King rejects it, demanding screams in death. The Deep Sea King defeats more minor heroes who challenge him.

Genos arrives at the shelter and battles the Deep Sea King, trading blows. The Deep Sea King rips off Genos's arm and damages him severely. As it threatens civilians, Genos orders evacuation, but the monster declares all humans its prey.

The Deep Sea King spits acid at a defiant child; Genos intercepts it with his body, shielding her but wrecking himself. It slams Genos through a wall, praises his injury (already healing), then prepares to finish him.

Mumen Rider crashes his bike into the Deep Sea King's back in "Justice Crash," then charges with punches despite the odds. The Deep Sea King toys with him, bashing him repeatedly before slamming him away.

Saitama catches the flying Mumen Rider just before he hits the ground.