Let's start off with the simple fact that none of this was Izuku's fault. Neither was it Hisashi's really. There's no way he could've known his quirkless son would break so hard in his final moments, and he definitely wasn't expecting the said boy to come back moments later and stick a sword in his abdomen like it was nothing—like he wasn't the powerful villain Dragon who had years of military training. Or for him to change so rapidly; from anger to at peace to prideful to cowardly to flamboyant. Izuku was sure his last thoughts were, "I've made a monster!"
And naturally, the little demon wanted to care for itself(or maybe for its other-selves). It rummaged through the house, grabbing things that were both pretty and valuable(and of course a diamond necklace from its deceased mother jewelry box, but Hisashi doubted that was for sale), clothes and food, and packed it all up in a bag and left.
And another fact, Izuku never lived past that day either. Or, at least he never saw another day, but his body was definitely alive. His mind, however, was locked away, but he could feel it. Every hit, every burn, every strain, every cut, he could feel it. And maybe that's what made him his current self, an almighty persona waiting to be let free.
But he wasn't needed, he never was, every one of his selves could handle themselves. So, instead of begging to be let free, he waited and felt. Every battle, every move, every plan, and eventually he knew more than any other-self. They deemed him όλα and vowed to never let him loose.
They moved to the richer side of the city and bought a large warehouse using a fake ID. They used it as their home, decorated it in all whites with their bed right in the middle.
They'd often write down notes to talk to one another, made sure to eat just enough for one person to stay fit, and tended to their wounds. They loved each other and they never even met.
Again, none of this was anyone's fault. But there certainly someone to blame.
