G-Shock's GA-2100, released back in 2019, picked up the nickname "Casioak" online almost immediately — watch fans noticed its octagonal bezel looked a lot like Audemars Piguet's Royal Oak, despite the two watches sitting on opposite ends of the price spectrum: roughly 10,000 to 70,000 yen for the Casio versus 900,000 yen and up for the real thing.

The joke came full circle in May 2026, when Audemars Piguet itself collaborated with Swatch on a "Royal Pop" model, watch-industry news described as the biggest crossover moment since Omega and Swatch's MoonSwatch.

This GA-B2100MF carries the same octagonal DNA in a fluorescent colorway, part of the Casioak family that started the whole conversation. It's sold out direct at CDJapan, reachable now through their Proxy Shopping Service.