In ponytail or pigtails, pleatherlike tops with puffy shoulders and iridescent black tulle skirts, the singers of Babymetal stood on individual six-inch risers so the crowd could see them properly. Behind them, onstage at the PlayStation Theater on Wednesday night, were the band’s musicians: two guitarists, a bassist and a drummer, all in white robes and white-painted faces, smiling broadly. The singers (Suzuka Nakamoto, Yui Mizuno and Moa Kikuchi) spoke in English with slight catches in their voices. What they said was, in order, “You make me happy!” And, “I’m happy because of you!” And, “I will never forget today!”

Babymetal is a Japanese idol group, which is to say a singing group put together by a talent agency — in this case Amuse Inc. — and one that trades heavily in kawaii, the Japanese concept of cuteness. Since 2014 the band has moved surprisingly fast internationally. Its second record, “Metal Resistance,” entered the Billboard albums chart last month at No. 39; it was the first Japanese act to make that chart’s top 40 in 53 years. (The album did even better in Britain, rising to No. 15.)

Every idol group needs a visual and iconographic theme, and Babymetal’s is metal, with a genial twist. The band members do not hold their hands up and throw devil horns; they connect thumb to middle and ring finger, extending pointer and pinky to make a sign of a fox, because they and their manager, Kobametal, have invented a creation story involving the mythos of a fox god who inspires them. In clinical terms, kawaii metal is a good idea: opposites. Light and dark, soft and harsh. “It’s a newborn genre,” Su-Metal told a BBC reporter a few weeks ago. Perhaps she’s right.

There is a general fantasy of innocence being served here, as there is in the entire kawaii culture. But there’s a specific kind of innocence too: artistic innocence. The band’s Wikipedia page says that none of the singers knew what metal was before joining the group. True or not, that fact seems crucial. There is a persistent cross-cultural disjunction in their music on record: It can seem like the work of two groups whose studio was double booked yet are somehow performing in sync. The disjunction continues when you see them live: They can almost seem not to know that a Casper-the-Friendly-Ghost metal band is headbanging behind them.