He was born there, she here. His gut language is English, hers Japanese. They understand each other well enough, but the 7 o'clock NHK Evening News divides them. (NHK translates its Evening News into 27 different languages.)
She prefers to listen in English as she is amused by the wooden straightness of NHK's take on the language. He, unamused by the English version, prefers to listen in the original Japanese, which while not at all elegant at least seems authentic.
And so over time they have devised their own language to use between them, bits of Japanese and bits of English, like an imaginatively flavored omelette.