During the fight with Deku and Shigaraki, (when AFO was in control of Shigaraki,) Deku had his arms decayed by Shigaraki’s quirk, ‘Decay,’ that makes anything that he touches crumble to dust.

Before this.

After AFO explained to Shigaraki how he planned every single thing of his childhood, he then took over his body. While this was happening, Simple Growth also responded to the lingering influence of Shigaraki’s personality by manifesting a hand mask on All For One’s face. All For One decided to move to the next stage of his plan….

Deku(Midoriya): “ALL FOR ONE!!”

After Deku tried to jump at All For One, he used Shigaraki’s quirk before he could touch him. The hand mask falling off

AFO:”Yoichi is gone.. My intermediate goal is foiled… Oh….? A lingering note..?”

The hand mask grew on his mouth again, making a weird fleshy sound.

“Be silent.”

AFO looked around for Deku with his eyes, spouting and thinking

AFO:”Are you dead yet, boy?”

Deku groaned and tried to get up

Deku(Midoriya): “All…. For…. One…”

AFO then spoke, looking down at him

AFO:”I’ll move on to my hollow, immaterial final goal.. That is to SAY- THE WORLD.”

Deku(Midoriya):”I won’t let.. you!”

Deku tried getting up but realized his arms were gone.. He didn’t cry since he broke his fingers and arms so many times in the past for being reckless. Everything that happened right now was live on TV, Midoriya’s mother watching horrified. Deku still wanted to fight. Out of nowhere, Sero came in and tried to wrap AFO with his tape, failing and getting thrown back. Ojiro was there too, trying to fight AFO with Sato.

You and Aizawa came through the Warp Gate of Kurogiri.

Aizawa: “Sorry for the delay..”