The reason all the English reviews are positive and all the Korean reviews are negative is basically gaming 'culture' in a very distilled form.
The English reviews are positive as most have never played White Day before, and it's a good horror game with a good amount of content and some legitmately scary bits. Most had never heard of it before, or heard of it but never played it, and like it. There were some bugs but they have very quickly patched and fixed many of them already. It's a pretty good and challenging horror game with some interesting design that stands out for many as it's different than many first-person horror games and has some fun old-school design elements you don't see too often these days.
The Korean reviews are from a very different place. In Korea, White Day was a very successful mobile game after the original 2001 PC game bombed. In Korea, White Day is literally the second top-selling paid mobile game of all time, it's become pretty popular there. The PC/PS4 version had delays and it released with a few bugs, and though they've been fixing them quickly Koreans are ragging they had to wait longer for this game due to a few delays and it still released with bugs. Also the Steam release is set to USD rather than the Korean Won, and though it has new content from the mobile version and various updates it's 4x more expensive for them than the mobile release to match the USD price, so many are whining about the price. Also because the game is popular over there, it also has attracted Korean trolls and complaining about pandering the game to dumb American audiences, along with some purists viewpoints of the original vs the remake.