Who is Tomoyasu from Extremely Loud and Incredibly Close and what is their importance?

A survivor of the U.S. atomic bombing of Hiroshima, Japan, 15 Aug. 1945, Tomoyasu talks on tape of searching for his daughter, Masako, and having her die in his arms. Tomoyasu makes the tape so people will realize there can be no more war. Oskar Schell plays the tape on his boom box for his class in school.