It is looking as though Dragon Quest Monsters: The Dark Prince has been a hit game in Japan as developer Square Enix has taken to social media platform X to say that the game has sold out in a number of major gaming stores. The Japanese company has urged fans to purchase the digital edition if they cannot get a physical copy of Dragon Quest Monsters: The Dark Prince at retail. We should find out the actual sales number for the physical edition on Wednesday when Famitsu reveals the Japanese boxed-software charts.
“Due to popular demand, the packaged version of “Dragon Quest Monsters 3 is out of stock at some stores. We hope you will consider purchasing the downloadable version.”

Had the same problem getting a physical copy of Pokemon Scarlet and Violet from local retailers, ended up getting it as digital with the intention of purchasing a physical copy asap.
It sounds like Dragon Quest Monsters: The Dark Prince has been quite the hit in Japan! With this level of popularity, it seems like the game has struck a chord with fans of the series.