Apparently, Lotus/Suu is a girl...

It's a really common thing to give young looking guys extremely feminine voices in anime, so I wouldn't be surprised if that's what they did here.

:u

I know, but that was just too feminine.
They better confirm Lotus' gender so people would stop being so confused...

EDIT: He/she does look kinda young, but not THAT young.
Unless of course, he/she just didn't go through puberty