Originally Posted by FriendlyFacez

Okay, if this is an actual thing with Nutaku’s newest update someone really needs to explain to me why I still only have my original slots open (150 after I upgraded it) for characters.

What they gave us all is UPGRADE MATERIAL STORAGE 200 for both CHARACTERS and EQUIPMENT. It's used for storing Ampy's, Manyu's and those Equip Upgrade items only.
When you are on the equip/lock tab you have an option to click 'move to storage' for manyu etc. When you do they go into the 'Storage' button in the top right of the equip/lock tab.