Konnichiwa Maciamo-san!

In Japan, family and family name are very important more than the West. The Japanese wish to continue their family name and they take pride in their family name. An instance, family name is the first and one's first name is second in Japan. And the Japanese call person by one's family name but not first name. You can become more familiar with Japanese if you learn about Japanese family name system.

I've also heard that it is possible for a husband and wife to choose a new family name for themselves (so that Tanaka-san and Yamamoto-san could become 2 Suzuki-san). Could anyone confirm or deny this ?
Yes, the Japanese can get new family name. But it is need to the important reason for changing family name. Because it is the cause of confusion if one can get new family name easily.

Usually the Japanese woman get husband's family name when she get married. But sometimes Japanese woman keep her family name and her husband get her family name by reason of she is an only daughter. If she will get her husband's family name, her parents lost their family name.

Do foreigners with middle names or composed family names have to give them up when they adopt Japanese nationality?
In Japan, Japanese government don't approve a middle name, one's name is only Family name and First name. But if you want to leave your middle name in Japanese family register, you only have to write your family name and middle name in blank space of family name. Your family name and middle name is regarded as one family name in this way but you can leave your middle name. But if you choose this way, your children must inherit this family name( and middle name). Of course this middle name is not children's parent name and you can not leave your partner's name as middle name.

NANGI