Japanese trademarks, like most outside of the US, are based upon date of first filing. In the US, it's based on first use, and filing is allowed only after it has been established as a bona fide brand.

Before McDonald's first went International, some punter had registered it in Japan, and they had to pay him a mighty fine sum to get it back. Prior use isn't relevant in most countries trademark law (it's like legal domain squatting, but in the real world!)