A row is brewing for control of Japan’s everything app.

Elon Musk might talk about building an all-encompassing app. Japan already has one. Having evolved from a WhatsApp-like messenger into a product that touches almost every aspect of society, Line is now at the center of a tug-of-war for control — and risks becoming the latest powder keg that threatens relations between Japan and neighboring South Korea.

Line was created by the Japanese unit of South Korea’s internet giant Naver, which still holds 50% of it in a complex structure overseen by SoftBank Group. But after a series of cyberattacks last year spooked Japanese regulators, discussions have begun about divesting Naver’s holdings and moving control of the service fully within Japan’s borders.