By MARI YAMAGUCHI
TOKYO (AP) — Japanese Princess Aiko, the daughter of Emperor Naruhito, has turned 20, ready for a debut as a new adult member to take a share of official duties for the royal family whose population continues to shrink under the male-only succession law. Aiko is the only child of Naruhito and Empress Masako, a Harvard-educated former diplomat. She is currently studying Japanese literature and says she is willing to help her parents by participating in royal duties. Aiko is not eligible to ascend the Chrysanthemum Throne. Under Japanese law, she also has to leave her family if she marries a commoner, just like her older cousin, Mako, last month when she married her college sweetheart.