We have just discovered that Konami has region-locked PES 2018 in China. As stats show that same country was making up 18.26% of their player base for PES 2017.
It is important to note that the game has a Chinese language pack, making the region lock even more confusing.
Other than China, Malaysia and India are also region-locked for PES 2018, which never happened in the previous installments.
Reasons for the region lock are still unknown. This is the screen that users from region-locked countries get when trying to access the game on Steam.
More info will be provided as soon as we get an update on this situation.