My Bathtime Secret for Japan's Summer and Winter

Japanese bath rooms are different from most Western bathrooms. For one thing, unless they live in a really, small, cheap apartment with a Toto brand boxed bathroom, Japanese people wouldn't ever want the toilet in the same room as the bathtub. Taking a bath is like a hobby in Japan, and having the toilet visible from the bath is terrible. Japanese people usually have a toilet room with just a toilet in it and a bath room that is divided between sink-and-mirror-area and bathtub-long-mirror-area by a sealed, frosted glass door. That sealed, frosted glass door can be very useful. In fact, that sealed, frosted glass bathroom door is the key to a pleasant or frustrating time in Japan during (the worst) two seasons of the Japanese year.
★Winter★

Keep that door open for a free home humidifier

A Japanese winter is cold and dry. The air is so dry and there's no central heating in most houses, so some days your throat can feel terrible in the morning. Air that's too dry isn't good for you. That's why, if you take a bath at night (or live with a Japanese person who does / most Japanese people I know take baths every night in the wintertime) you should keep the bathwater in the bath and leave the bath-room door open. The mirrors near the bath room all fog up and the air gets a lot more bearable to breathe at night because it's got more moisture. Remember to let the bathwater out in the morning unless you want to be scrubbing the sides hard every night.

★Summer★
Close that door unless you want hundreds of gross new roommates

Cockroaches are a fact in most areas of Japan during the summertime. You'll see them on the sidewalk and very often, in your house. I turn into a very, very neat person in the summer to minimize my chances of attracting them. Japanese cockroaches are big. Then, my friend told me about a great trick. If you live on the first, second, third or even fourth floor of an apartment building, you'll likely have a problem with cockroaches in the summer. The older your building is, the likelier you are to have cockroaches in the summer. What most people don't know is that the main way they get into the house is through the drains in your sinks and in the bath area!

If you keep that sealed, frosted bath door closed during the summer, the cockroaches may enter the bath area through the drain (don't keep your toothbrush in the shower area unless you don't mind taking the chance) but they won't be able to access the house because the door will be shut and they can't get through the seal. It's great. You can also buy special mesh nets to go over the kitchen sink drain so that they can't come in. When my roommates and I started vigilantly keeping the door shut this summer, we noticed a great improvement! I only saw two cockroaches in my house the whole summer!