Ok so I've tried to edit the .lua. It's not working.
File edited: data\lua files\skillinfoz\skillinfolist.lua
Or are there more files to edit?
Ah nvm, found the solution here: http://rathena.org/board/topic/64362-some-skill-cannot-up/
Thanks anyway.
a separated storage per character, per account, so it is 1 storage for 1 character in that account. other character can't access the other character's storage.