How to unlock new game+ and additional characters?

[Katarn]

I beat the game and got achievement for it, but I don't see any new characters on the selection screen. If I click "new game", then there is no "new game+" or what should there be, it just starts a new game with the same default characters.

[KiYoRoxS]

At the character select screen you have to press RB

[Weekend Kid]

When you are in character select, look at the top of your character. There is a second window and you can select different characters in it.