It wasn't safe to talk about it at the office, or over email. But in a private room in one of Tokyo's karaoke bars, representatives of Japan's biggest insurance companies gathered -- not to sing, but to coordinate a price hike on a shared corporate client.

It was 2022, and the insurers were reeling from a series of costly natural disasters including heavy rains and typhoons that required billions in payouts and decimated their balance sheets. In a frictionless market, each insurer would have looked at the worsening storms, assessed the growing risk, and raised prices accordingly.