Tomohisa Yamashita
The theme song is "Seishun Amigo" by Shūji to Akira, a special group consisting of KAT-TUN's Kazuya Kamenashi and NewS' Tomohisa Yamashita, named after their drama counterparts. The song topped the Oricon charts in 2005, selling over 1 million copies and climbing to the top as the most successful single of the year.