"It's only recently that people have come to see original manga drawings as objects of value. Traditionally, publishers sent the drawings back to their creators after printing and left it up to the cartoonists to decide what to do with them. There was no custom of preserving the drawings. Experts say when cartoonists die, relatives often throw the drawings away".
https://www3.nhk.or.jp/nhkworld/en/n...ckstories/753/