Yuta’s “metal arm” is basically a cursed tool/metal arm casing he can attach with Rika’s help, and he uses it to boost the power of his punches in close combat.

Quick Scoop

It’s not usually portrayed as a permanent robot arm. In the Jujutsu Kaisen material, it’s described as a steel arm attachment stored with Rika that covers his whole arm and reinforces his striking power.

Why he uses it

  • It gives him extra close-range force.
  • It fits Yuta’s flexible fighting style, since he swaps between swords, cursed techniques, and physical attacks.
  • In the Sendai fight, it was used as part of his arsenal against Takako Uro.

Forum chatter

A lot of fan posts call it a “robot arm,” but that’s more shorthand than canon accuracy; the lore explanation is that it’s a metal shell/cursed tool, not a true mechanical prosthetic.

Bottom line

So, Yuta has the metal arm to make his punches stronger and to expand his weapon options in battle. If you want, I can also explain when he first used it or how it works in the Sendai Colony fight.