Couples in Japan have hit upon a way to retain their individual surnames after marriage: They don't get married.
Instead, they create a "de-facto marriage" by separating from their respective parents' family registers to create their own, while skipping the step of registering their union. This little subterfuge has made Hiroyuki Ito of Toyonaka the "unregistered husband" of wife Ayuri Yuasa.
Yuasa's motto is a "cheerful de-facto marriage," and she told those around her, "Ours is a de-facto marriage." An acquaintance of her parents congratulated her, saying, "I do not know whether that is called a marriage. Anyway, Congratulations!" [Link]