he earned a bachelor's degree in mathematics from keio university in 1998, a master's degree from keio in 2000, and a phd from keio in 2001, researching the lovasz–woodall conjecture under the supervision of katsuhiro ota. after temporary positions at vanderbilt university and under the supervision of paul seymour at princeton university, he became an assistant professor at tohoku university in 2003, and moved to the national institute of informatics in 2006.