The game is apparently rated 18-and-up, due to, according to our Kotaku tipster, Ni no Kuni, the in-game casino. In Ni no Kuni, there is Las Vegas style city, where players can play card games and slots.
As The Korea Times pointed out, gambling is a sensitive area for South Korea, especially after recent nationwide gambling scandals. Gambling laws have already caused headaches for other game developers, such as Blizzard with Diablo III, and they seem to be why an all-ages title like Ni no Kuni is getting slapped with an adult rating.
Ni no Kuni is a collaboration between game developer Level-5 of Professor Layton fame and Studio Ghibli, the anime maker behind classics like My neighbour Totoro.
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