幸福な少年 (Koufuku na Shounen)

Background
"Koufukuna Shounen" is an original song by Kururingo featuring GUMI, Kagamine Rin, and Hatsune Miku.

This song has entered the Hall of Fame. It is featured in the album V Love 25 -Fortune- and Kirakira Ringo (きらきらりんご).