Japan's biggest breakout musical act of 2017 wear polar bear masks. The duo AmPm debuted this past spring, cloaked in fuzzy headgear and withholding all biographical information. In just over six months, the pair have had their easy-breezy electronic music released via Dutch label Armada Music and performed to thousands in Indonesia, sharing the bill with pop heavyweights DNCE and NCT 127.

If you've never heard of them — or are wondering how you could miss two polar bears manning a set of decks — don't worry too much: AmPm's success can't be seen on any traditional chart or even YouTube view counter.

Rather, the dance-pop duo's success has played out almost entirely on the streaming service Spotify, pushed on by non-Japanese listeners. The group's debut track, the mid-tempo "Best Part Of Us" featuring singer Michael Kaneko, broke a million plays within 10 days of hitting the industry-leading service. Subsequent songs have topped the million mark too, while Japanese articles focused on AmPm's success note how more than 90 percent of plays for its songs come from abroad.