Saipan used to be very popular with Japanese tourists, because it's only about a 4-hour flight from Tokyo. Then the Japanese economic bubble burst and that dried up.

FWIW, I visited once in 1998, when Japanese tourism was trailing off but hadn't completely collapsed yet, so flights & hotels were cheap. It was a bizarre but largely uninspiring combo of the worst of strip-mall America (McDonaldses, K-Marts) with mass tourism (huge, slowly decaying hotels and beachside hucksters). The snorkeling was OK and the beaches were pretty, but dotted with rusting WW2 tanks...