That whole shop is nearing the end of line. There are too few customers. We have never seen anyone but the MC, the idol, and the turtle. The turtle didn't even use the services. Realistically there should be a bunch of others, as only two paying customers wouldn't even allow the owner to pay the bills, let alone make profit. But nevertheless, the owner will probably only keep the place running as long as there's a washing machine still in a working order, then shut it all down. Not enough income to repair devices or overhaul the place.
Edit: Of course there's non-zero chance it's a yakuza money laundering business, but it would need to be stupid yakuza to allow the place to get so near to termination. Although with the Japanese police's infamous incompetence, who knows. The yakuza could probably lock the doors permanently and still keep laundering money through it, as long as the place still exist, even if it had zero revenue.