What kind of wrench is used for these kinds of nuts? I bought this bicycle in Japan and would love to change the tires by myself instead of going to the shop.

I’m assuming the other side looks quite different. Likely these are tamper/theft resistant skewers and need a special wrench. Many bike shops have at least some of those wrenches in their tool box. If you want to replace these with standard QR skewers the shop you buy them from may be able to remove them for you.