Okubo was born inKanda, Fukuoka on 9 June 1982. After graduating from high school, he joinedJ1 League clubCerezo Osaka in 2001. He played many matches as forward and offensive midfielder from first season. However Cerezo finished at the bottom place in2001 season and was relegated toJ2 League. In 2002 season, he scored 18 goals which was the second top scorer and Cerezo reached the second place and was returned to J1 in a year. From 2003, he scored more than 15 goals in J1. He was also selectedAsian Young Footballer of the Year award in 2003.
In 2005, Okubo moved toLa Liga clubMallorca on loan. Although the club results were bad, Mallorca finished at 17th place and remained La Liga in2004–05 season. Although he played many matches as substitute forward in2005–06 season, his opportunity to play decreased from April 2006.[2]
In June 2006, Okubo returned toCerezo Osaka. At then Cerezo won only one of 13 matches and at the bottom place of 18 clubs in2006 season.[3] Although he played as forward all matches excluding suspension, Cerezo finished at the 17th place and was relegated to J2 again.[4]
In 2007, Okubo moved to J1 clubVissel Kobe. He played many matches as left midfielder in two seasons under managerHiroshi Matsuda and scored more than ten goals both seasons.
On 3 January 2009, Vissel Kobe announced Okubo's transfer toVfL Wolfsburg of theBundesliga.[5] After just six months with Wolfsburg, he returned to Vissel Kobe. Upon his return, he became the first Japanese striker to have won the Bundesliga title.
In June 2009, Okubo returned to Japan and re-joinedVissel Kobe. He played as forward all 19 matches and scored 8 goals in 2009 season.[6] Although his opportunity to play decreased for injuries in 2010, he played as regular player until 2012. However Vissel finished at the 16th place in2012 season and was relegated toJ2 League.
After Vissel Kobe was relegated to theJ2 League in 2013 season, Okubo transferred toKawasaki Frontale. An ever-present figure and a regular starting eleven in Kawasaki, he scored 26 goals in his debut season in theKanagawa Prefecture football club and clinched top scorer of2013 season. He played more than 30 matches every season and he became a top scorer for 3 years in a row until 2015 season.
In 2003, Okubo was selectedJapan national team by managerZico. He made his international debut on 31 May 2003 in a friendly againstSouth Korea atTokyo National Stadium when he was sent on to the pitch to replaceTakayuki Suzuki.[10] Although he played many matches as forward in 2003, his opportunity to play decreased from 2004 as he struggled to score goals under Zico.[10]
In August 2007, Okubo was selected Japan for the first time in 2 years by managerIvica Osim.[10] Okubo scored his first international goal on 17 October 2007 in a friendly againstEgypt atOsaka Nagai Stadium.[10]
In 2010, Okubo was selected Japan for2010 World Cup. He played as left midfielder in all 4 matches[10] and Japan qualified to the knockout stage.
Okubo's selection for the2014 World Cup in Brazil was the big surprise of coach Alberto Zaccheroni's squad announcement. The forward had previously played just once for the coach in four years.[11]
