Ninjas Arc

This stretch of the story sits nineteenth in the overall run and fourth within the Neo Heroes Saga. Three threads braid together across it: a stubborn recruitment bid by Flashy Flash, the buried past of the Ninja Village that raised both him and Speed-o'-Sound Sonic, and the surprise return of Blast to the Hero Association. A private sparring wager eventually spills over into a clash with the divine servants of God.

Convinced that Saitama could reach untapped heights under his guidance, Flashy Flash keeps turning up at the apartment while Saitama games with King. He finally lands a deal: a bout on Flash's own grounds where losing makes Saitama a disciple, but landing a single blow inside half an hour buys his freedom. Saitama shrugs off every strike and closes in for a hit until Genos cuts things short with word of a monster alert.

Elsewhere Heavy Kong, Bone, and Peach Terry are losing ground to the Internet Surfers when Sonic is spotted looking on. The arrival of Saitama, Genos, and Flash, followed by Gale Wind and Hellfire Flame, sparks a tense four-way face-off. It ends fast: the Surfers fall in a blur, Saitama plants Sonic in concrete, and Flash routs the two elemental fighters into retreat.

Wanting no part of the rival-and-pupil act, Saitama tracks down Manako himself, sketching her for King and trapping her with his help. The group resolves to reach Sitch and summon Blast, only to find Blast already waiting at Association Headquarters. He ties the Ninja Village that raised Flash to God, and warns that its master, referred to only as That Man, has stirred back to life.

Sonic, cornered by Wind and Flame, is instead greeted by the full Heavenly Ninja Party. These graduates explain that the village's collapse loosened its rule against fellowship, then lay out their design: kill Flash, remove Blast, and seize the world. They order Sonic to bait Flash to a chosen spot. Flash, meanwhile, confesses that on his graduation day he slaughtered everyone at the village save Sonic, and he answers Sonic's letter of challenge.

The former friends duel until the Ninja Party breaks in, branding Sonic a traitor. Guided by Overgrown Rover's nose, Blast reaches the scene and flattens the whole party without a single killing. He then teleports the group to Sonic's hideout, where Saitama sits beside a human-shaped crater. It is Empty Void, the village's leader, already knocked out off-screen. When a rip opens in the sky, two divine beasts, Byakko and Genbu, burst from the Rift in Spacetime as guardians of God.

The beasts level whole blocks until Blast raises a shielding barrier. Saitama, cradling Rover, leaps to strike them but is diverted by the waking Void. Void and Blast together put the guardians down and send them home, and Void's monstrous face splits to reveal the human beneath, cleansed of God's grip. Blast asks Saitama to join the coming war and departs with Void through a portal to the Rift, where they discover the corpses of Byakko, Genbu, and a third beast, Kirin, plainly Saitama's doing.

Empty Void sheds God's corruption and rejoins Blast as his ally. Sonic and the Heavenly Ninja Party learn of God and the mysterious cubes for the first time, which pushes Sonic to resume training beside Flash. Blast's assigned station, the Rift in Spacetime, comes to light: he guards it to keep God's creatures, including the divine beasts, from reaching Earth. Having watched Saitama strip God's power from its pawns, Blast formally requests his aid for the final reckoning to come. In the days that follow, the Heavenly Ninja Party trails Saitama with near-religious zeal, pestering him to lead them.