This is extremely misleading. The death rates among evacuees was not significantly different from the death rates among the general population in the same time frame. Dig into the stated causes of deaths and it's usually vague things like "exhaustion".

Out of 300k people 1,400 died over the span of 6 months [1]. Assume everyone lives to 100 and a uniform age distribution (both of these are actually generous: life expectancy is lower and age distribution skewed older in Japan), and 1500 people dying in 6 months is exactly on the mark for old age deaths. Even more telling, actually try and click on the link to the primary source in Mainichi Shimbun and it 404s.

1. https://www.nbcnews.com/news/world/fukushima-evacuation-has-...