Billing themselves as "Toy Gun and Military Goods" this looks to be a tiny Japanese Airsoft/Army Surplus shop in Japan. They carry many products also seen at other retailers like Straightline Collectibles. These boots may be the exact same as Straightline Collectibles' Boots. Judging by the size availability it's nearly certain that they're the same boots.
Kokkado lists their boot's sizing as: 25cm, 25.5cm, 26cm, 26.5cm on their official website and the Rakuten website meaning the sizing is VERY small by western standards. Their largest size of 26.5cm = US Size 8½