Newly elected Prime Minister Naoto Kan began his political career when he became involved in civic movements, and attracted attention for his sharp manner of speaking in the Diet.
At one point, he was forced to step down as president of the Democratic Party of Japan over failing to pay into the national pension system for a period of time. After serving in more low-profile posts, Kan has risen again, this time to prime minister.
He participated in student protests while a student at Tokyo Institute of Technology's School of Science and worked for civic movements after graduation.
Kan's first brush with the world of politics came when he supported Fusae Ichikawa, a women's rights activist, in her 1974 bid for a seat in the House of Councillors.
In 1980, he ran for office himself and was elected to the House of Representatives on the ticket of the now defunct Socialist Democratic Federation (Shaminren).
In 1996, Kan became health and welfare minister in the cabinet of then Prime Minister Ryutaro Hashimoto, formed by a coalition of the Liberal Democratic Party, the Japan Socialist Party and New Party Sakigake. During his tenure, he brought to light documents that had been concealed by his ministry concerning HIV infections caused by tainted blood products. This brought the spotlight on him for the first time.
When the DPJ was formed in 1998, he became its first president, and has been known as one of the "faces of the party," along with outgoing Prime Minister Yukio Hatoyama. While president, Kan brought about a 2003 merger with the Liberal Party, then led by Ichiro Ozawa, the outgoing secretary general of the DPJ.
When the DPJ came to power in 2009, Kan was appointed deputy prime minister and state minister in charge of national policy in the Hatoyama Cabinet. He became finance minister in January and left the position of national policy minister.
However, he has been criticized by some DPJ members for distancing himself from key issues, including the relocation of U.S. Marine Corps' Futenma Air Station.
Kan is known for sometimes having a short temper. His sharp words during Diet deliberations led to the nickname "Ira-Kan" (short-tempered Kan).
His hobbies are go, shogi (Japanese chess) and mah-jongg. When he was a university student, his intense love for mah-jongg led him to invent a machine that automatically calculates game scores, for which he obtained a patent.