Complex sentence: Marriage between a Japanese and non-Japanese person was not officially permitted until 14 March 1873, a date now commemorated as White Day, although marriage with a foreigner required the Japanese national to surrender his or her social standing.
Split into simpler sentences: Marriage between a Japanese and non-Japanese person was not officially permitted until 14 March 1873, a date now commemorated as White Day. Marriage with a foreigner required the Japanese national to surrender his or her social standing.