Since the age of 7, Japanese schoolboy Shun Sasaki has been offering free guided tours to foreign visitors at the Hiroshima Peace Memorial Park with a mission: ensuring that the horrors of nuclear war do not fade from memory with the passage of time.

Now age 12, Shun has conveyed that message to some 2,000 visitors, recounting in his imperfect but confident English the experiences of his great grandmother, a hibakusha who survived the atomic bomb.

"I want them to come to Hiroshima and know about what happened in Hiroshima on Aug. 6," Shun said in English, referring to the day the bomb was dropped in 1945.