Why has wedding of Japan's Princess Mako still not gone ahead?

Plans still on hold after revelations about finances of would-be groom's mother two years ago

They have been together since university, their emotional bond apparently stronger than ever despite being separated by an ocean and a continent. And they have the blessing of a likely future emperor.

But for Japan's Princess Mako - the eldest daughter of the first in line to the Chrysanthemum throne - and her boyfriend, Kei Komuro, the sound of wedding bells has grown more distant in the three years since they made their relationship public.