This is the only one for cleaning water stains! I found a cleaning product called "Scotch-Brite Bath Shine Bath Sponge with a Recess" at a drug store and bought it.
Detergent-free bath sponge developed by 3M Japan. As the name suggests, a part of the sponge is dented, making it easy to hold firmly with your hands. Since it bends smoothly, it is easy to fit in places such as the curved surface of the bathtub, the handle of the faucet, and the handrail of the bathroom. It's a slight difference, but it feels easy to clean the entire area around the water.
Another feature of this sponge is the hybrid structure with "double power". The microfiber part removes hot water red and slime, and the film part removes soap scum. When I tried rubbing a faucet or shower head that was dirty with water stains, it turned into a shining innocent state. I couldn't handle the dirt that was left for a long time, but if I use it to clean it even once a week, it seems that I can prevent stubborn dirt.
The approximate size is 15.5x8.8x5.1cm. It's a little big for people with small hands, but how about using it for cleaning around the water? The selling price at the drugstore I went to was 429 yen (tax included).