According to this NYTimes article, he was a manager at the Japanese nuclear reactor site hit by the tsunami. The article reports on a set of videos just released which document the chaos at the site over some days. But, if I read it correctly, Yoshida was onsite, doing his best to direct workers, getting bad advice and orders from big shots who were ignorant, and generally being a good bureaucrat by this definition: when the environment the bureaucracy was designed to handle goes berserk, a good bureaucrat does her best. Two paragraphs:
At one point in the videos, as conditions at Reactor No. 3 are deteriorating, raising fears of an explosion, Mr. Yoshida sends a team of workers out from the bunker with this message: “I’m truly sorry. Please proceed with the utmost care.”He later suggests that if the situation does not improve soon, he and some older workers will consider “a suicide mission” to pump water into the reactor, a decision officials at headquarters said they would leave to him.