Before becoming a professional, Sakai was majoring in medical science at Kyoto University.

For a long time, Sakai was the strongest amateur player in Japan, and when he won the World Amateur Go Championship in 2000, the Kansai Ki-in awarded him professional 5 dan (after defeating two 5 dan and two 7 dan players).

He was also the first player in Japan to be awarded a special 8 dan (amateur) diploma.

In 2010, Sakai won the Gosei title, defeating title-holder Cho U 3–2.

This biographical article relating to a Japanese Go figure is a stub.