To unlock the other characters games you have to:
1) Play Tecna, Flora, and Stella’s games.
2) Talk to Bloom.
3) Play any of the three games again.
4) Talk to Bloom again. She’ll tell you Musa has arrived.
5) Play Musa’s game, then talk to Bloom again.
She’ll say she has “two surprises” for you, which are Aisha and Roxy.