The thing about being an idol, about being Johnny's, is you don't get to choose. You don't get to choose what you do, what you sing, what you wear, and you don't get to choose who you're paired up with.
It's not like forming a band with your friends or even forming a band with strangers, because at least then you'd have some say. Instead you're told you're the same age and have the same name and are from the same place, so you're stuck with each other.
It's like an arranged marriage, is what it is, and here you are almost twenty years later, still together in more ways than one. You have your own thing and Koichi has his, but you're still KinKi Kids (you will always be KinKi Kids, you know, whether you're together or not) and, more importantly, you're still Koichi and Tsuyoshi.
And that's what makes it worth it, all the things you hate about being an idol, all the things you hate about being Domoto Tsuyoshi. Without all that, you wouldn't be lying here on his sofa listening to him work out the melody of a new song.
You close your eyes and let it wash over you and as the song takes shape, you sing along. It's disjointed and random and you know someone else will write the lyrics anyway, but that's okay. For now it's yours. The world can have the final polished product, but this moment will always be just yours and his.