When the two of them train alone in a quiet gym and there is no one besides them. After practicing some serves and receives, Kageyama was about to go home but Hinata stopped him then said

"Kageyama, how about we sing a duet?"

"oh, what song?"

"em...wide awake, how does that sound?"

"hm, okay who's first?"

"can i?"

Kageyama just nods and waits for Hinata to start the agreement Hinata: "i'm falling from cloud nine~" Kags. : "i'm wide awake" Hinata: "Thunder rumbling...Castles rumbling~" Kags. : "i'm wide awake" Hinata: "i am trying to hold on~" Kags. : "i'm wide awake" Hinata: " God knows that i try seeing the bright side" Kags. : "i'm wide awake" Hinata: "i'm not blind anymore!~" Kags. : "i'm wide awake...oke good singing boke!"

What they didn't realize was that they weren't the only ones there but Tanaka and Nishinoya were standing near the door