Can my characters sing?

First of all, I will say: Eric absolutely does sing, but whether or not he's good at it is debatable. But he lowkey sings the song "A you're adorable" to Mira in his comments throughout the study puzzle

Akira Ishida - Secret ~Dakera no Message

his seiyuu is Akira Ishida so this is the best approximation I can give you

unfort the puzzle sections of Zero Escape are unvoiced so lol

Yoosung also sings in canon, and that one IS voiced

Mystic Messenger (Yoosung's Lullaby)

so here is him singing in character

He sings a few other times too, more energetically in those, but I don't have the clips

his VA has a few more songs

Yoosung singing☆ | Mystic Messenger

성우 심규혁의 '이적 - Rain' (Yoosung voice actor singing)

Mystic Messenger~" Little Kitty" w/ V, Yoosung, and ...

this one isn't really canon to Mysme but all three actors were from it so the person set it up like that lol

I think this is probably the best clip for his energetic voice

Suzaku's voice actor, Takahiro Sakurai, does not sing very much but here is him singing a Disney song

Takahiro Sakurai When You Wish Upon A Star

I'm guessing you'd be hard pressed to get him to sing in canon unless it's season 1