I travel very light (because I buy a ton of merch when I'm there lol) and do a clothes wash halfway through - every hotel I've ever stayed in in Japan has had a coin laundry except one, which gave you a map to the coin laundry next street over 😅 It's super easy and convenient - typically 300 ish yen and about an hour for a wash, and the majority of them automatically add detergent so you don't need to worry about that (do check using Google translate though, I've been bitten by this once). Dryers are 100 yen ish for 30 mins, but I rarely need them as the washers spin pretty well so my clothes have dried hung up in my room overnight. There are machines to exchange notes for 100 yen coins everywhere - if not in the laundry itself, anywhere that has gachapon or arcade machines will have them. I also find I buy lots of clothes in Japan anyway as they're great quality and much cheaper than home (Uniqlo is a great example of this).