#IM SORRY. MONCHAN.

[mishy-mashy]

Theory: All For One gave Tomura the Decay Quirk

I was thinking this for a while. Midoriya learned that Tenko was originally Quirkless, already being five, so there was no way for him to have the Decay Quirk; All For One gave it to him

Isn't it awfully convenient that right as Midoriya wonders "Who is this guy?", that All For One showed up?

All For One knew Tenko was a blank slate without a Quirk (yet, or at all).

Going back to ch. 235, we see that after Tenko was playing heroes with other kids, he got walked home by a man in a suit

Suit, shadowed face, hat, tall, and Tenko still has black hair? This matches this memory, and we can see there's a lot of shading in the palms

All For One walked home Tenko. He could've given him a Quirk during that time. Right after he brought him home, Kotaro got mad that Tenko was playing and talking about heroes. Already, while Kotaro is upset at him, we see Tenko scratching. According to Nao, his allergies got worse, and if he was just given a Quirk, his allergies could've been fueled by the new Quirk as his body adjusts

Even if it's just a mutation, we do know that his itchiness was related to Decay, since the itching went away after he destroyed what he didn't like (his Quirk revolves around de-constructing and destroying, so natural leanings toward those urges, etc)

Yes, Tenko's Decay may very well just be a mutation like Eri, but I just want to bring one more thing to attention about the theory (All For One gave Decay when walking Tenko home):

When Tomura used Decay and was fighting Re-Destro, back when he only had Decay, Machia was in shock, because it reminds him of All For One long ago. Not only his figure as a ruler that Machia remembers, but All For One could've done the same thing as Tomura (Decay), long ago