Masao Yoshida, the man whom many credit with preventing an even larger nuclear disaster during the 2011 Japanese tsunami, died on Tuesday from esophageal cancer.
He was 58.
Yoshida volunteered for "suicide" missions, while also refusing government orders to stop cooling nuclear reactors at the Fukushima Daiichi power plant, The New York Times reported.
By pumping sea water into reactors to cool them, he likely prevented explosions that would've eclipsed even the 1986 Chernobyl meltdown.
According to Russia Today, when Yoshida defied orders and continued to cool reactors, he prevented an explosion that could have rendered "the whole of northeastern Japan ... uninhabitable for decades, if not centuries."
As it was, roughly 100,000 people were forced from their homes to flee nuclear material released by the damage.
Yoshida took command of the situation from a bunker inside the plant after a 42-foot tsunami slammed into the plant's six reactors on March 11, 2011.
Video released last year by Tokyo Electric showed Yoshida deftly, calmly directing his employees even when the circumstances appeared dire.
“I fear we are in acute danger,” Yoshida said, according to The Times. “But let’s calm down a little. Let’s all take a deep breath. Inhale, exhale.”
Before the disaster, Yoshida was head of nuclear facilities and admitted being "too lax" when it came to building tsunami walls.
He was in charge of Fukushima Daiichi for less than a year when the earthquake struck, triggering the tsunami.
Yoshida remained in charge of the recovery at the plant for just a few months before leaving in late 2011 due to illness.
Officials say there's no link between his cancer and his work at the power plant.
Yoshida is survived by his wife, Yoko, and three sons.
To this day, Tokyo Electric Power Company continues to release water quality reports from the site.
On Wednesday, the company said it has measured some of the highest levels of cesium-134 and cesium-137 in groundwater samples.
"We are continuing to tackle this problem in such manners as to intensely bring forward implementation of contamination prevention measures," the company says on its website.