Ryutaro and Kosuke, having started music production around the same time (winning a musicianship in BEMANI to appear in beatmania 4th Style ) had always had a strong collaboration, even at a friend level.

kors k usually handle hard style beats while Ryu☆ used a happy style. This eventually brought them to mix their work.

Early collaboration between can be first seen in the album 'teranoid underground edition' under a song where they showdown "Pumpin' Rabbit Express", although they were referred to as "Ryu☆ vs teranoid".


The name "The 4th" is likely derived from starting their careers in beatmania's 4th Style.