hmm I had also wondered about that and I have no idea. It would be awesome if it would just make him permanent but keep his level from the leash. Though knowing gogames I doubt it will work as we want it. It could also just give an error that you already have recruited the partner, so you have to dismiss him and then use him. Or they didn't think about it and you will have 2 White Ichigos :p
Please let us know what happens if you use him.
EDIT: Oh pretty awesome that they keep the level
Post time 2015-9-29 13:27:27