Time Travel

Whoever holds this power can journey into the past or the future, though every recorded instance has carried the user backward rather than forward. Only two individuals are known to wield it, Saitama and Garou, the latter accessing it while locked in Cosmic Fear Mode.

One route to the technique has the user picture their own inner universe, understood as reaching an intense state of focus while steering the particles inside their body. Once every particle within them flips into an anti-particle, they begin sliding backward through time, passing into a tunnel-like realm where warped images of bygone events hang like windows. Moving through the window that matches a given moment and place delivers the user to that destination. Rewriting the past reshapes the timeline in turn, an effect the story calls Reversal of Causality, especially where the Ominous Future is concerned. A lingering puzzle surrounds Genos's core from the original timeline, which Saitama somehow carries into a present where Garou never killed Genos or any other hero. Rather than overwriting, merging with, or vanishing alongside the present core, it coexists with it, letting the current Genos tap the memories and data it holds and become the only one aware of the erased Ominous Future. Saitama clutching the core throughout the journey may account for the anomaly.

After reaching Cosmic Fear Mode, Garou gains the power to bend his body's particles at the subatomic level and force them to act as anti-particles. Though the feat is supernatural, he frames it as the ultimate technique of his martial arts, and he concedes that he has not truly mastered it for time travel. Even so, hints suggest he manages it to a degree, most notably when Tareo is roused by what seems to be Garou's soul drifting in from the Ominous Future and slowly fading, as if he has returned to say goodbye. Garou passes the technique to Saitama after his defeat, hoping the hero can master it and undo the Ominous Future born from their battle. God kills Garou mid-attempt and reclaims his powers, yet Saitama still reproduces the leap and travels back, returning to the instant Garou first appears before the heroes in Z-City and felling him with one punch before any disaster can repeat. The success immediately fuses Saitama with his present-day self, leaving a single Saitama who retains no memory of the Ominous Future or the technique.