I found out by chance on Twitter. I haven't been there, but it's definitely this place. The supermarket model may also be the Maruetsu on the same site. Huge thanks to 胡簶ヌ🏝-san for giving me the opportunity, and to Ichiru-san for telling me it exists! In Matsudo too, if one explores more, there may be new locations (or there were).
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