Chapter 8 — The Deep Sea King
A pack of monsters calling themselves the "Clan of the Seafolk" arrive on the shores of City J intent on invading the land. When the hero sent to fight them is defeated easily by the Deep Sea King himself, Saitama and Genos head for the city to help.
Other chapters
- Chapter 1: The Strongest Man
- Chapter 2: The Lone Cyborg
- Chapter 3: The Obsessive Scientist
- Chapter 4: The Modern Ninja
- Chapter 5: The Ultimate Master
- Chapter 6: The Terrifying City
- Chapter 7: The Ultimate Disciple
- Chapter 8: The Deep Sea King
- Chapter 9: Unyielding Justice
- Chapter 10: Unparalleled Peril
- Chapter 11: The Dominator of the Universe
- Chapter 12: The Strongest Hero