[2] Tsuboi was educated at and played for Yokkaichi Chuo Kogyo High School and Fukuoka University.

[4] Tsuboi represented Japan for the 2001 Summer Universiade held in Beijing where the team won the title beating Ukraine in the final.

Japan's national coach Zico gave him the first cap in 2003 when he played Tsuboi on 11 June 2003 in a friendly against Paraguay at Saitama Stadium.

[5] In Japan's first match against Australia, he suffered from cramps in his both thighs and had to be replaced by Teruyuki Moniwa in the 56th minute.

He was also in the squad for 2007 Asian Cup but did not play any game in the tournament as Yuki Abe and Yuji Nakazawa were the first-choice centre backs.