Wait a second. People think AFO killed Yoichi on purpose, in a jealous rage of 'If I can't have you, no one can'?
[Who are you?! Get away from him!]
AFO looked at Kudo and wanted him to get away from Yoichi.
AFO, in his own head, seems to be telling Kudo that Yoichi belonged to him. That 'Look at me' could have been directed at Kudo rather than Yoichi, or both of them.
[If you stop being mine... then-]
AFO is realizing Kudo is again, taking Yoichi away from him, this time right in front of AFO. Kudo is holding Yoichi's hand. It sounds more like AFO is panicking here
Rather than thinking of the narration being toward Yoichi, what if it's toward Kudo the entire time?
Imagine the below in the context talking toward Kudo rather than Yoichi
1. AFO doesn't know who Kudo is, and wants him to get away from Yoichi
(this also implies terrible security or something because how does AFO not know who Kudo is? Kudo took his most valuable person two months ago. Maybe Kudo and Bruce literally killed their way to Yoichi and left no witnesses?)
2. AFO proclaiming that Yoichi is his, not Kudo's
3. Insisting to Kudo that Yoichi belongs to AFO
4. AFO getting mad that Kudo doesn't look at him, when everyone always looked at him when he showed himself, even back as a Meta orphan (read: threat)
5. AFO's fear or panic because Kudo is taking his first gift (Yoichi)
So, this is my interpretation of what happened here, because AFO puts focus on Kudo:
Yoichi was behind Kudo when AFO aimed at them!! Yoichi was the slower runner that Kudo was dragging along, so if AFO aimed for Kudo, he would have hit Yoichi first! And that spatial Meta sure doesn't look like a grabbing-type!
AFO is jealous and possessive, sure, but he never imagined a world without Yoichi. He literally describes it as [the world lost all color] when he felt Yoichi's Factor shatter. Yoichi was his only attachment for living; his reason to live.
AFO is extremely co-dependent to Yoichi. He might even think they're one and the same, being twins / half of each other (their original Factors imply All For One [the Quirk] was something that could've been passed down, but had split into two). He doesn't care about life if Yoichi isn't in it.
So why would he ever go down the 'If I can't have you, no one can' route? AFO would have given Yoichi all the allowances in the world to be alive, no matter how many times he ran away or fought back.
To AFO, he wants Yoichi with him. He even went through the trouble of finding a weak-enough Factor that even Yoichi could take. I don't think AFO ever saw Yoichi's death as a possibility. He'd lock him up, let Yoichi starve himself, knew Yoichi was frail, but it never occurred to him that Yoichi might die.
AFO gave Yoichi a Factor - something known to be physically-taxing and possibly incompatible - when Yoichi was on hunger strike in the vault. That should have killed Yoichi, in my opinion.
AFO never imagined Yoichi's death as possible. He blamed Kudo, clung to Yoichi's leftover hand, chased down a Factor across generations, and was so in denial that he repressed the memory of who really killed Yoichi.
AFO is vague and twists stories a lot. His narration here is purposely vague by the author, because it can be addressed to Kudo or Yoichi, or both
It's already been mentioned that vagueness regarding OFA is on purpose. AFO and his background is very closely-tied to OFA.
In the first panel, it's only Yoichi that AFO sees. The moment Kudo shows up, AFO addresses him instead. Narration is toward Yoichi and Kudo, but in the final panel, where both of them are gone, the narration cuts off.
Once Yoichi vanished, Kudo himself also vanished. AFO only saw the hand that was left behind.
An example of AFO changing the narrative to fit what he wants it to be:
The line about his tears is AFO about when he killed Kudo, right after Kudo told him that AFO was the one who killed Yoichi.
AFO cried in silent rage / grief, AND THEN CLAIMED IT WAS SO A DEAD GUY (KUDO) WOULD BE CONFUSED???
KUDO SMILED HE DAMN KNEW WHAT WAS GOING ON THE WHOLE TIME. HE DIED WITH A VICTORY OVER HIM (different from the other victory of getting Yoichi's Factor away)
This is the most honest we see AFO narrate anything relating to Yoichi. AFO isn't a reliable narrator; he writes himself up as a cool, evil guy who has complete understanding and control of everything he's ever done ever. And here, we see what's likely the most 'real' we get of him. AFO is panicking, confused, and sounds like a kid.
2. To me, AFO is basically a chuunibiyo who never grew out of his phase, because he was never allowed to grow up properly, whether by society (lack of support systems) or by himself.
He calls himself 'Demon Lord'. He refused to read the comic book ending because he didn't like the Demon Lord (his favorite character) losing. He named himself 'Zen', which to me feels like the equivalent of first-time-OCs named 'Yuki' or 'Ebony'. He monologues all over the place about how evil and amazing and smart he is.
(All Might even calls him out on trying to be cool. I point it out more in the latter half of this post)
Isn't the chuunibiyo phase something about wanting to be something greater than you are, trying to prove your importance, and needing attention from people? That's what it looks like to me, at least.
3. Unrelated at this point to the post's main point (AFO didn't mean to kill Yoichi) I also think AFO is autistic. Someone else made an amazing post about it that convinced me, but I can't find it. Something about how he's extremely particular, only wears one type of clothing (suits), hates when things don't match what he thinks they were, forces his narrative so it matches what he thinks it should be like, his default expression is blank, having to learn how to facially-express emotion and not smiling until he was like 12, being nonverbal when Yoichi himself had learned to talk by then, hitting Yoichi back because it's only fair and he thought it was the rational response when you didn't like something,
-having a huge obsession over a comic book series to the point he shaped his entire life and identity upon it, genuinely putting in effort to learn how to interact with people and behave like a normal person while Yoichi understood mercy, empathy, and the benefit of the doubt from a young age (lack of social interaction may have also been a factor here though) , being all 'look at my friends / followers, Yoichi! They all love me!' and Yoichi going 'You've manipulated them' or something- a lot of stuff, y'know
AFO did not kill Yoichi on purpose. He would never kill Yoichi on purpose. Nor was it out of 'If I can't have you, no one can'.
AFO may have been focused more on Kudo / was narrating toward Kudo the whole time (purposely vague on the addressed target)
AFO aimed for Kudo, but misfired because Yoichi was behind Kudo when AFO aimed
Yoichi is AFO's reason to live. Why would AFO purposely kill his sole attachment to life?
AFO is an unreliable narrator, but was pretty honest when he accidentally killed Yoichi.
AFO is an eternal chuunibiyo