It happened last month. An arrest has been made. From a Chinese news report:

TOKYO, Nov. 21 (Xinhua) -- Police arrested a man Friday for allegedly detonating explosives last month at a cultural hall of Japan's largest lay Buddhist organization, Soka Gakkai, and at a separate building housing a local Japan-China friendship association, both in the city of Tokushima in Shikoku, the police said.

Takaaki Hori, 35, a resident of Tokushima, is suspected of placing and detonating explosives in the entrances of the Soka Gakkai cultural hall in the city and the Tokushima-China Friendship Association on Oct. 13, Kyodo News Agency reported.

No one was injured in the blasts, which damaged doors, windows and ceilings in the buildings.

After the explosions, a document claiming responsibility for the blasts was found in the entrance of a separate building housing the publisher of the Tokushima Shimbun newspaper and JRT Shikoku Broadcasting Co., the police said.

Hori has told investigators that he used firecrackers to make the explosives at his home and that he took the claim of responsibility to the press building, they said.

Soka Gakkai is known as the main base of support for the New Komeito party, the junior coalition partner of the governing Liberal Democratic Party.

Disturbing to say the least.

The last line suggests that the bomber's actions were somehow related to Soka's government connection. Anyone have more info?