the only way to kill yama-jii is to steal his bankai, with his bankai, he's invinsible,
and they can't steal it yet until they know it's limit.
so my first question is, is north the limit of his bankai?
2) how come renji can have his bankai stolen and ichigo can't?, they released their bankai at about the same time
3) how come toshiro hitsugaya can have his bankai stolen, doesn't he also have room for improvement?