CareerToy started as a duo of Yoo Hee-yeol and Yoon Jeong-oh and was named after their two initials 'Y', as in Two + Y = Toy.But after releasing Toy's first album, Yoon Jeong-oh left the band to study overseas and Yoo Hee-yeol joined the navy for his mandatory military service. Yoo Hee-yeol has been the sole member of Toy since 1996.After his discharge from military service, Yoo released Toy's second album Fairy Tales for Adults. The title song Remember I Was Next to You sung by Kim Yeon-woo became a big hit and the album was a success.In 1997, he released the third album Present and also started a record label named Toy Music (currently Antenna Music). After a six-year hiatus, in 2007 Toy released the sixth album Thank You with the title song '??? ??(A Passionate Goodbye)' featuring vocals by E Z Hyoung.