Iida Kunihiko was born in Manchuria in 1942, but was soon brought to Hiroshima by his mother. There he experiences and survives the atomic bombing in 1945…
This story was created by the NPO 平和の大切さを伝える日本語教材をつくる会 which I would translate as ‘Association for the creation of Japanese language teaching materials to convey the importance of peace’. Iida Kunihiko is a real-life witness of the era and collaborated with the NPO on this story about his life.
The grammar in this story is mostly です/ます in short sentences and therefore really easy for intermediate readers. However, it does make use of more specialised vocabulary to talk about the war and the hardships that followed after. You will learn some new words easily as the more difficult words are annotated in the margin and translated into English.

When it comes to talking about the 20th century wars, I believe the most important thing is giving voice to those who experienced the worst of it. I was pleasantly surprised to see this association’s effort to write about an atomic bombing witness’ life in easy Japanese, so that learners could read up on this piece of history.
You can read this story here: https://tadoku.org/japanese/book/4163/#bd-look-inside
Length: 13 pages