For whatever undisclosed reasons, Chihiro's official Youtube channel has uploaded two concert recordings: the first one is CHIHIRO ONITSUKA『TUNE HOUR 2016』originally broadcast on Ustream on January 28th, 2016 (why is this the first time I hear of this performance?!), and the second one is the first stop of her syndrome concert tour at CLUB CITTA on April 13th, 2017. The syndrome performance is filmed with a static overhead camera, and the sound is recorded on the camera's microphone (so not the highest of qualities), this is not the official recording that ended up on DVD.
Chihiro sounds pretty ok in the first one, and she actually sounds great in the syndrome performance! So check these videos out if you feel inclined (or if you're in need of background music like I am).
Live Streaming Archive: CHIHIRO ONITSUKA『TUNE HOUR 2016』 (28.01.2016)
Live Streaming Archive: Chihiro Onitsuka Concert tour 2017『syndrome』(13.04.2017, CLUB CITTA)