Despite panic stories and concern among the public and the media, Yoshida was a classical stoic Japanese and stayed at his post. 8 months later he was admitted to the hospital and was diagnosed with throat cancer. After surgery for that, he had a brain hemorrhage and surgery again.
Was Fukushima to blame? Not even in the Rachel Carson mythological world where you can spray DDT in your basement and get cancer and die 6 months later. The radiation levels were not that high and such radiation exposure would manifest itself in that way in 5-10 years.
So let's blame his smoking.
“We don’t have the US army fire trucks we need but at least we have got smokes,” he joked while passing out cigarettes to workers in a heavily used smoking room beside the bunker during the disaster.
Heroes aren't always soldiers or firefighters or Spider-Man, sometimes they are guys who just keep calm and do their jobs while the media and the executives at the company above him are losing their minds.