Sauce: https://e621.net/posts/3875865?q=tro_pikaru

Rouon Aro is a singing synthesizer voice bank. Meaning he is a voice source to make music with. Here are some examples (oh and he is a cute guy):
https://youtu.be/eUAZuUmIlJw
https://www.youtube.com/watch?v=Hy4R9dCJvSU