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It's a unique Japanese practice. Each year in Japan there are tens of thousands of unusual adoptions – very different from adoptions elsewhere in the world.

They're mostly of grown men, adopted by their wife's family, so that they can then take over the family business and keep the family name alive.

Mariko Oi has been to Japan to investigate.

She meets, among others, a famous Kabuki performer and the owner of a spa hotel, who runs the world's oldest family business.

(Image: A crowded street in Japan Credit: Getty Images)