She absolutely lipsynched.
It's just not really possible to sing that way.
It's not an amateur way, it's just really simple
I guess it's possible that they could have dubbed over the concert...but honestly, I think that ayu would know if she could sing that way or not, and she most likely just lipsynched it.
She probably did another recording before the concert.
I don't mind. I actually really like that performance. I never really listened to the song before it.