AU where Yuuji’s muscular body, his strength, and his headstrong attitude made absolutely EVERYBODY believe that he’ll present as an alpha, and so they told him all his life that he will become an alpha, raised him as an alpha, and socialized him as an alpha

Only alpha uncle!Sukuna knew better, but he knew no one would believe him if he’d point out that Yuuji was destined to be an omega, and he also keeps quiet for his own purposes later on 👀

So when Yuuji inevitably presents as an omega, it’s a complete disaster because Yuuji (for VERY understandable reasons, given how he was raised) behaves in the least omega-like manner possible. He refuses to accept the idea that he’s any different than he was before just because he’s an omega, so he continually keeps on behaving like an alpha, bringing endless shame and scandals to his family, and lowering his marriage prospects as a wife

So eventually, at a loss and knowing that Sukuna is the only one equipped to handle such a naughty, rowdy omega like Yuuji, they give Yuuji over to Sukuna, under his complete control, so that Sukuna could train him to become a good, proper omega 😵‍💫❤️

And of course, at the very end, Sukuna ends up taking Yuuji as his own wife 🥰 After all, by the end of that training, they may as well have been mates, given how close and intimate the training was, especially in the later phases when they (finally) progressed past Yuuji’s rebellious phase ❤️❤️