This was the last song of many in the Live concert so even though she was starting to run out of steam she powered through like a boss. And no, her identity is still left a mystery, although I've heard some people in the front row could see her face
As other comment mentioned, she still hides her identity and as how she got discovered/started, she began uploading music covers from vocaloids songs and it wasn't until she released her og song "Ussewa" where her popularity exploded to the skies. Up to this day she still uploads cover songs. Ps. There is a clip online where she reacts to this exact same performance and is hilarious cause she cringe at herself 🤣
you're correct that usseewa is what skyrocketed her popularity, but it's worth mentioning that her covers and guest features on a couple songs were enough to land her a record deal with universal music japan, of which usseewa was her debut single under them
Unfortunately, this is the only Ado live performance video we have so far, although there are multiple videos of Ado singing her songs in live streams on youtube where you can also hear her raw voice. The good thing is that there are still many Ado songs you probably haven't heard. I recommend The World's Continuation, Eien no Akuruhi, and FREEDOM. There are also Ado features that are bangers but aren't on her channel like Rasen and Shikabanese by jon-YAKITORY. I hope you can react to them.
Much the same has been done for many years of her career, which began in 2011 with another superstar of the Japanese music scene - AIMER. Even in 2019, her live concert recordings were photographed in such a way that you could hardly see her face. Japanese specialty?
Ado sounds like Hana Yomeguri, who is also a Vtuber and also a singer. Hana speaks 7 languages and streams here on RU-vid. It would be great if you listened to her and gave your opinion of the similarity of their voices.
Ado is an Utatite which is a NicoNico term for Faceless Singer. People who do songs on NicoNico without showing themselves. This is the reason she continues to hide her face. But Ado’s message about Japanese norms could be a thing too because in Japan a lot of singers are Idols whos image is important as they need to be appealing physically as well as conceptually for people. This results in the music industry basically controlling their diet, social and romantic relationships, hobbies, etc Ado has a lot of self-esteem issues. So that could also play a part into it.