The battle royale of battle royale game developers is about to begin. Instead of taking place on a shrinking map, though, this one is going to happen in a Korean courtroom. PUBG Corp., the studio behind PlayerUnknown’s Battlegrounds, has filed a lawsuit against Epic Games for copyright violation over its game Fortnite.

A PUBG Corp. official told The Korea Times that the company has filed an injunction against Epic Games Korea with the Seoul Central District Court, alleging copyright infringement. It seems a bit strange to see one company suing another over making a similar game – who would sue who for the countless open-world games? – but the relationship between  PUBG Corp. and Epic Games is a more complicated one. When Fortnite originally released, it released as a pay-to-play game focusing on a player-versus-enemies mode called Save the World. In this mode, you built structures and traps to defend against an oncoming horde of zombie-like enemies. In September of last year, though, the company added a free-to-play battle royale mode and even called out the studio’s love of PUBG as an inspiration for making the new mode. Fortnite‘s new mode, simply called “Battle Royale,” caught on and has spread like wildfire, with people playing on console, PC, and mobile devices. Further complicating this is the fact that PUBG‘s game engine, Unreal Engine 4, is a product of Epic Games, the company also making Fortnite.

PUBG Corp. parent company Bluehole has been looking since then at how best to address Fortnite‘s very existence.

“We’ve had an ongoing relationship with Epic Games throughout PUBG’s development as they are the creators of UE4, the engine we licensed for the game,” Bluehole vice president Chang Han Kim said in a prepared statement. “After listening to the growing feedback from our community and reviewing the gameplay for ourselves, we are concerned that Fortnite may be replicating the experience for which PUBG is known.”

Further, PUBG Corp. is concerned about Epic Games using PUBG‘s name to promote its own game.

“We have also noticed that Epic Games references PUBG in the promotion of Fortnite to their community and in communications with the press. This was never discussed with us and we don’t feel that it’s right.”

There’s a lot for the courts to examine once things get started. With Epic providing the engine for PUBG, they have a unique power over their competitor. Epic could pull support for Unreal Engine 4 or withhold crucial technical support from PUBG Corp. that could be seen as allowing Epic a competitive edge over PUBG Corp. That Epic called out PUBG when promoting Fortnite is an issue, too. In an environment where it’s just two artists riffing off one another, it looks like credit where credit’s due, but when we’re talking about companies as big as Epic and Bluehole – also taking into account that provider-customer relationship – it looks more like Epic is riding off the coattails of one of its customers and taking advantage of that customer’s popularity.

If the lawsuit succeeds, it could have implications throughout the game industry depending on how everything rolls out. It could set precedent for companies to go after each other over similar game mechanisms, modes, and features. It could also affect the way Epic Games works with the countless other game developers to which it licenses Unreal Engine 4.

The suit will likely be a long, dragged-out battle, but we’re curious to see how this affects both games in the long term. Are you still playing PUBG, or has the Fortnite fever grabbed you?