Last year, two of my friends went through 離婚 (rikon, divorces). Both told me they waited until their children became adults to avoid any legal troubles as it seems that a 国際離婚 (kokusai rikon, international divorce) is much harder than a 国際結婚 (kokusai kekkon, international marriage).
The Ministry of Health, Labour and Welfare keeps track of 国際結婚 and has logged 夫妻の国籍別にみた年次別婚姻件数 (fūsai no kokuseki-betsu ni mita nenji-betsu konin kensū, the number of marriages by nationality of husband and wife by year). Almost 3% of marriages over the past 10 years have been between Japanese and foreign nationals.
The statistics track the nationalities of non-Japanese spouses, and among the most common are 韓国人・朝鮮人 (kankoku-jin/chōsen-jin, Koreans), 中国人(chūgoku-jin,Chinese people), フィリピン人 (filipin-jin, Filipinos), タイ人(tai-jin,Thai people), 米国人 (beikoku-jin, Americans), 英国人(eikoku-jin, British people), ブラジル人 (burajiru-jin, Brazilians) and ペルー人 (perū-jin, Peruvians).