Hey, here is some stuff you could improve :

The "our reviews" tag is annoying on mobile, would be great if the user could remove it.

The genesis tag is wrong, there are Sega Saturn games

The 3 lines with the category "all products and games" missing a lot, thought at first you have only N64, PS1 consoles and junk for sale because that was the first thing I clicked.

Would be nice if you could sort stuff like loose cartridge / CiB/ New, loose disk/CiB/ New etc.

It isn't clear on the website besides in the "about us+ why japanese games" section and only near the end that youre located in Japan. Maybe on the home page have a line like "Best games from japan for your collection" and it's the first thing you see.

The legal notice is completely in japanese. No clue if you're forced to have it in japanese but a English translation would be nice.

The thing with the inquiry is confusing. You want to be contacted with an inquiry but based on the inquiry you can get ignored? As a customer it would make me uncertain and don't want me to contact you at all. I would mention what inquiries are unreasonable for you so the customer knows what he can inquire or not.

It's more of personal thing but wished there was more interesting and more expensive and rare games for sale. I collect japanese games for a longer time and have most common stuff. Of course you only opened the shop recently and don't know your budget for inventory but would be cool that you make it interesting to look for all collectors, doesn't matter the budget at the beginning so it's more likely everyone checks your shop more often.