The majority of Japanese home washing machines run with only cold water. They are usually not accompanied by a dryer, so clothes and towels hang outside to dry, while unmentionables hang in an indoor room with good ventilation. As you can imagine, this is a good energy-saving step (or, as we say in Japan, "eco," pronounced echo) for the environment. However, if you need their services, there are a lot of dry cleaners in Tokyo, and a few around Ikata as well.
Since there isn't exactly a lot of space in people's homes for mounds of dirty clothes, families have to do the laundry every day. When you meet your host family in Ikata, you will certainly have some dirty clothes from your travels. Don't by shy; your host mother will expect you to give them to her. If you wait until the next-to-last day and then empty your backpack to reveal 14 days' worth of unwashed clothes, they probably won't be completely dry in time for your flight. (Not to mention, what mother likes that kind of surprise?)
To avoid unnecessary rough handling by the machine, people put clothes and linens inside mesh bags before washing them.
While I have heard stories from other people about clothes ripped up by a washing machine, I've never had that unfortunate experience myself, and I like to think it's because I religiously protect my garments in mesh bags. The worst that I've ever encountered was a couple of times when clothes came out with a bleach stain.
The bottom line? The unadventurous would be well advised to leave expensive, one-of-a-kind, absolute favorite clothing behind… or at least out of the washing machine.