This is a live performance - albeit in a very controlled environment.
From the About section:
A microphone and a white studio. And 1 rule. You’ve got 1 TAKE. Perform anything you like. Show us everything you’ve got for that 1 moment. THE FIRST TAKE
This song also happens to be the opening theme for the Japanese animated show Demon Slayer: Kimetsu no Yaiba. I watched an episode and got bored, but I absolutely fell in love with Aimer. I especially recommend her album Open a Door from 2023.
It’s a really cool concept and their execution of it is top notch! :D