Japanese-style slippers are footwear designed to be worn in the house. Thus, it is important that the soles are light and soft. The benefits and comfortability will differ depending on what materials they're made from. Generally, plastic or felt soles are most commonly used.
Both have the characteristics of being easy to use inside the house due to their light nature, doing minimal damage to wooden flooring and tatami mats. Plastic soles don't pick up dirt and grime easily but some people might find the pitter-patter noise they make when walking to be irritating. Felt soles make little noise and are also very soft to the touch.
These different types of soles each have their own characteristics. In Japan it's not uncommon to have these different types of slippers prepared depending on the environment they're going to be used in. We're making every effort to educate customers on the softness of the soles of slippers via videos and other materials on the internet.