Don't be mistaken, I cannot read Japanese.
I can read Katakana and Hiragana and have just enough understanding of the Japanese language to interpret what they are saying.

If I can read 15 Kanji without the help of Furigana in total, that's really pushing the count.
However if I think what you mean, that is unlocking the levels you can set for your opponents in the versus mode.
Basically saying, in the versus mode you fight your opponent at the level you are at the default setting.
But unlocking that you can choose your opponent's level.
IE. your level 1 Warrior of light vs. lvl 100 Cloud or your lvl 93 Shantotto vs. lvl 1 Judge Gabranth and so forth.