WARNING: The following contains spoilers for Jujutsu Kaisen Chapter 178 "Sendai Colony, Part 5," by Gege Akutami, John Werry and Snir Aharon, available in English from Viz Media.
Yuta Okkotsu has been an anomaly since his introduction in Volume 0 of Jujutsu Kaisen. From the immense amount of Cursed Energy he possesses to the fact that he's distantly related to Satoru Gojo, he's also one of only four Special Grade Sorcerers recognized by the Jujutsu community. Fans have long known how powerful Yuta is compared to his fellow Jujutsu Sorcerers. In fact, he was declared the second strongest Sorcerer after Gojo as recently as Chapter 173.
Despite this, his powers remained a mystery and have never really been explained -- until now. There's been a lot of speculation about what Yuta's Cursed Technique might be; some have even argued that, like Yuji Itadori, he may not have one at all. However, it would be odd for someone as powerful and renowned as Yuta to not have his own Cursed Technique -- and there were definitely hints at it in the past.
In Volume 0, which the Jujutsu Kaisen 0 movie adapts, Yuta was able to use Toge Inumaki's Cursed Speech technique after watching him. It wasn't clear how this was possible and it was never actually acknowledged. Some readers guessed it must've had something to do with his Cursed Technique, while others believed it's something he can do because of his immeasurable Cursed Energy. As it turns out, both theories are pieces of the complete answer.
As the three-way death battle between Yuta, Ryu and Takako continues, the latter deduces what Yuta's Cursed technique is. She initially assumes he's just a Cursed Speech user with Shikigami Jutsu when he uses the inherited technique of the Inumaki clan. However, she quickly realizes that's not the case when he uses Dhruv's Cursed Technique as well. This leads her to believe Yuta's his technique is "Copy," the ability to mimic other people's techniques. While "Copy" is indeed a technique he uses, it isn't his Cursed Technique.
Yuta's Cursed Technique is actually Rika, and it can store Cursed Energy for him. He is able to copy Cursed Techniques seemingly unconditionally while connected to Rika through his ring. Moreover, this connection grants him a Cursed Energy supply from Rika and allows the Cursed Spirit to completely manifest. He's only able to maintain a sustained connection for five minutes, but these details answer a few longstanding questions -- while simultaneously raising new ones.
One such question is what happens if Yuta doesn't have his ring on him or if it somehow gets destroyed. Will he no longer have the ability to copy Cursed Techniques? Exactly how crucial the ring is to his connection with Rika and his abilities remains a mystery at this point. Even those abilities aren't all he's capable of, as Chapter 178 ends with arguably the story's most epic cliffhanger to date. Yuta, Ryu and Takako all cast their Domain Expansions at the exact same time.
This has never happened before in Jujutsu Kaisen. Even two characters have never pulled out their Domain Expansions at the same moment, let alone three. Readers are hyped to see how this will play out and what each of these characters' Domains are. Yuta is only the second Jujutsu student after Megumi to use Domain Expansion thus far.
While Megumi's Domain is still incomplete, it's hard to imagine Yuta has that same issue. After all, pulling out an incomplete Domain in this situation -- against the Domains of two powerful and ancient sorcerers -- would likely result in his being overwhelmed.