Chain is the Sixth studio album by Japanese boy band KAT-TUN and was released in Japan on February 22, 2012 by J-One Records. On January 13, KAT-TUN endorsed the mobile game site "entag!" which used KAT-TUN's album track "Smile for You" as a CM song and the first-ever KAT-TUN animation, "Ai wa KAT-TUN", voiced by KAT-TUN themselves, was launched on entag! site for a limited period. Ai wa KAT-TUN hit 1,000,000 views in just 2 weeks.