Not entirely, at least for those who play the game (which ended part 6 of the main story on New Years) But I love when they use the irl lives as animation for the anime🥰 They did it for Vibrato when the boys performed NATSU☆Shiyouze using futage from the Riunion live from 2019 too!
It's "Let's go! Gaku! Tenn". (行くよ!楽!天!). And it's not in the game. SatoTaku (the VA of Ryuu) revealed it in the weekly radio show he does together with the VA of Gaku and said that it was his private choice to say it. Contrary to how it is implied in the game, he felt that he was not alone standing there, but they were there together with him. So he absolutely wanted to say it. And later on, they adapted his performance to the Anime. ...I'm crying every time I hear that section of the radio show...