From what I understood, being born twins in the jujutsu world meant splitting powers. Like Mai said, they were considered one entity/person. In order for one of them to acquire the “full form of a jujutsu sorcerer”, the other had to die so the powers/abilities could be transferred.
I hope that cleared it up a bit better :)
Ohhh that makes more sense thanks for explaining I understand why Mai had to die but damn gege killing everyone huh
I’m glad I could help :) and yeah seriously, this Shibuya arc has been one hell of a ride lol
Can someone explain what happened when they were in the domain please T^T