Let's have concubines?

From The Telegraph:

A Japanese prince has shocked the country with an attack on plans to let
women ascend the imperial throne.
Prince Tomohito, 59, the emperor's cousin
and fifth in line to the throne, became the first member of the imperial family
to speak out on the issue when he called on the nation not to abandon
tradition.
(snip)
But in a newsletter for the Imperial Household Agency, Japan's equivalent
of Buckingham Palace, Prince Tomohito wrote: "Is it really good just to alter
history and a unique tradition simply because we are living in the Heisei
[modern] era?"
Conservative monarchists believe imperial blood flows only
through the male line. Though Japan has had eight empresses, they served as
regents until the line could revert to a son born in the male line.
Prince
Tomohito wrote: "The reason the imperial line is so precious is that it is an
undeniable fact that male succession has continued without exception in an
unbroken line for 125 generations of emperors from the first reign of Jimmu in
the mythical era."
The prince outlined ways to preserve male succession by
bringing distant cousins of the emperor back into the line of succession either
by adoption or the creation of new royal houses.
Even more controversially,
the prince suggested male members of the royal family could once again take
concubines to ensure a supply of sons.
"I'm all for it but this might be a
little difficult considering social climate in and outside the country," he
wrote.