a literal translation is
"You're now able to use all of the characters!
The real battle is from here on out!"
minor detail is that it does not literally say 'all of the characters,' it uses a english-japanese word 'maikyara'(my chars). i'm assuming 'my chars' means the characters you see in the selection screen(thus "my characters" from the perspective of the player); a word like that is defined in-game for use in the game(might be a common gaming term; if so i wasnt familiar with it).
i wouldnt have explained that if there wasn't a chance someone might point it the special word and say 'well, there could be characters not in the category of 'my chars' that can be unlocked!' which is more than unlikely.
