As some have predicted, we now have confirmation of the flow state being a factor in this world. As
@Brackass explained, it's a real state that - while more apparent and commonly linked to sports, can be achieved through other means. I can't say I agree with the usage here; I've experienced the flow state many times over the years and it's never been for as brief as Isagi displayed. His goal honestly feels more like a "click" moment than being in the flow state.
After all, the flow state is only achievable when the person's skill level and challenge presented align perfectly, which - by definition - would require at least some time to recognise said difficulty in comparison to skill level. Isagi was always a step behind and was aware of that fact, placing him firmly within the "overwhelmed" and "concerned" groupings. For him to enter a state of flow under the current match's circumstances, his skill level would need to increase enough to push past the "excitation" grouping into the flow state.
Instead, Isagi's increase in skill seemingly comes from entering the flow state itself, rather than reaching the flow state after improving. He's gotten the order wrong - at least according to Csikszentmihalyi, and so I'm a tad annoyed he has a click moment and Ego is over there calling it the flow state. I'm passionate about the concept, so I'm willing to admit I'm too invested in a faithful representation.
Genuinely curious as to others' experiences with the flow state in terms of duration because I don't know anyone who has just snapped in and out of it as quickly as Isagi apprently did, all in all it was less than a minute.
Personal gripe: It gets to me when the flow state is introduced in sports manga and everyone is surprised at its existence, since there isn't a single sport I've played where someone has been surprised when it gets brought up.
All that said, I will lose my shit if we get a "Hyperfocus vs Flow" matchup. Seriously, I live for those clashes.
Edit:
@Kanami-chan, not sure if you're grouping those wrong on purpose or not, but an adrenaline rush isn't comparible to the flow state, and "the zone" is just another term for the flow state.