Somewhere out there is a beautifully tragic universe where the stars are aligned and the timelines matched up to where In-ho and Gi-hun experienced their first games together. No "Young-il," no lies, no deception. Not between them, at least. The two of them meeting at their lowest. In-ho being a bit on the reclusive side, keeping to himself mostly at first, simply observing from afar, but he can't help but be drawn in by Gi-hun, the latter's trusting nature balanced by In-ho's suspicious tendencies, and vice versa.
In this universe, Il-nam still presents In-ho with the knife the night after the dinner. In-ho still goes through with it, kills everyone while they're asleep in their beds. Well... almost everyone. He saves Gi-hun for last out of a foolish sense of sentimentality, but he hesitates too long.
Gi-hun wakes. They struggle, fighting until the guards intervene and separate them. (Il-nam pitting his two favorite players against each other.) Gi-hun stares at In-ho with hatred burning in his eyes, but In-ho doesn't try to justify what he's done. He deserves the full extent of Gi-hun's wrath. Part of him welcomes it even.
Then, during Squid Game, Gi-hun proves more resilient than he anticipated. Once he gains the upper hand, In-ho is bracing for him to deliver the killing blow, except it never comes. Gi-hun calls to end the games like he does in canon.
And when Gi-hun offers his hand out to him, something inside In-ho shatters.
Because he's seen the worst in In-ho. He's been betrayed by him. In-ho knows that forgiveness is not on the table, yet Gi-hun still chooses to believe that there is good in him nonetheless. There's that familiar spark in his eyes, that stubbornness that In-ho mentioned reminded him of his wife. Gi-hun isn't giving up on him. And for a moment, he's blinded by this man, this light in the darkness. In-ho knows he should take advantage of the moment, that he should turn the tide and kill him. Victory is so close that he could almost taste it.
But he can't bring himself to do it.
Instead, he takes Gi-hun's outstretched hand.