It was released on June 6, 2007, and became KAT-TUN's fourth consecutive number 1 on the Oricon singles charts with more than 300,000 copies sold in its first week.

Though Jin Akanishi appeared in the music video for "YOU", this song is the first official single to mark his homecoming after a six-month hiatus which he spent studying English in Los Angeles.

[2] Tatsuya Ueda and Yuichi Nakamaru first performed the song live when they were guests on Shounen Club on June 3, 2007.

In its first week of release, "Yorokobi no Uta" debuted at number 1 with 300,396 copies sold knocking off L'Arc-en-Ciel's "Seventh Heaven" from the top spot.

It stayed on the charts for 5 weeks and has reportedly sold over 373,965 copies and was later certified Platinum by RIAJ denoting over 250,000 shipments.