Carey kicked off her Elusive Chanteuse World Tour in Tokyo ... and based on the video -- as well as multiple others online -- it's clear she couldn't hit the high notes she's famous for.
During some portions of the concert, it seemed like Mariah forgot the lyrics ... however it's possible her microphone gave out -- since the stand broke during her performance of "We Belong Together."
Heartbreaker.
Follow me on Twitter and Instagram: @effiongeton