I made a post about this topic before, but I just wanted to ask this on a separate post,

What level does Ibaraki have to be in order for you to be able to hold 3 bottles at a time?

My Ibaraki friendship level is currently 20, but i'm still only able to hold 2 bottles at once.

And the wiki doesn't have any specific information on this too so...

I think you may have to get Ibaraki to level 22. It should unlock at level 19 if you have Amaterasu's +1 Bottle Collector (Amaterasu level 22). Correct me if I am wrong.