Toji got behind Gojo when Gojo briefly let his guard down and deactivated Infinity after assuming the immediate danger had passed. Toji then used a cursed tool that could nullify Gojo’s technique, which is why the stab actually landed and bypassed Infinity.

What happened

  • Gojo was already exhausted from staying on alert and maintaining his technique for a long time.
  • Once they were inside the school’s barrier, Gojo turned off his technique for a moment.
  • Toji used that opening to appear behind him and stab him from the back.
  • The later, decisive part of the fight involved the Inverted Spear of Heaven, which cancels cursed techniques and let Toji hit Gojo directly.

Why it worked

Gojo’s defense normally makes him hard to touch, but it depends on his technique being active and on him reading the threat correctly. Toji exploited both conditions: surprise, and a weapon that could shut the technique off.

In one line

He didn’t just “out-stab” Gojo; he caught Gojo off guard and used a technique- nullifying cursed tool to bypass Infinity.