He was born in Japan, but lived most of his early childhood in Shenyang, Liaoning when northeast China was colonized by Japan during the Second Sino-Japanese War. His father was working in a paper factory when they lived in China. Chiba's family lived in the attic of a work-acquaintance of his father until they could find a way to get back to Japan.

A long time ago, in a magazine called COM2, I drew a manga about myself. In the manga, I'm sitting at my desk, trying desperately to think of a good idea and then when I finally come up with something, I enthusiastically draw it. But then, when I look back at it, I think "Ah, this is so boring" and I go to sleep... It was really fun to draw!