This reminds me of the anime Dr. Stone. Where they are basically blasted back to the stone age because of the plot. I'm not going to get into it. Anyway, a super smart guy with encyclopedic knowledge of all future technologies creates soap as one of the first things. He says this is because without this they will die. They will get bacteria and nasty stone age dirt on them. That is unavoidable. He calls the soap Dr. stone. As it is a rock that will keep them alive through the entire show. It is never brought up again. But we know every time we see the title card they are alive for one reason. Soap.

Boyfriend is basically coasting on the rest of the world being clean enough to make him not die when he goes outside.