Japan's Prince Hisahito is celebrating his 19th birthday, becoming the first male royal in the country to reach adulthood in 40 years.

Given the imperial family's dwindling numbers, he could also be the last.

The elaborate palace rituals to formally recognise Hisahito as an adult on Saturday are a reminder of the bleak outlook for the world's oldest monarchy.

Much of this comes down to its male-only succession policy and dwindling numbers.

Hisahito is second in line to the Chrysanthemum Throne and is likely to become emperor one day. He is the nephew of Emperor Naruhito.

After him, however, there is nobody left, leaving Japan's Imperial family with a dilemma over whether they should reverse a 19th-century ruling that abolished female succession.

A first-year at Tsukuba University nea

See Full Page