Countdown to Japan: What clothes to bring?

I leave for Japan in 3 days. I am just now starting to pack. I wanted to wait until I can get a better grasp of what the weather will be like in Tokyo while I'm there.

Well, it appears that it'll be raining the entire time (and mostly in the 70s).

I don't mind the rain. But now I have to reconsider what clothes to bring. For my ten-day-trip, I have planned on only bringing: 
  • 2 pairs of pants (dungarees in khakis and navy) 
  • 2 button-up long sleeves shirts (oxfords in white and chambray)
  • 2 sweatshirts (in gray and blue)
  • a bunch of underwear, socks, and plain white tees
  • 1 pair of shoes (gray with brown pipping)
It's very basic/preppy. And while it seems like I'm not bringing enough clothes, I will be staying at places where there are laundry facilities and yukata/kimonos are provided. I also factored in that I  would probably end up buying clothes anyway. I fully intend on traveling with only a backpack for my luggage. However, I was not accounting for that I might get soaked. 

So, what should one bring on a trip like this?

Do people still wear slouch beanies? (illustration by @iamcallen)
One thing I learned from my last international travel was to not wear anything that absorbs odors easily. That means, no wool or cashmere unless I'm flying on a private plane.

Which probably will NEVER happen and can only dream about. But who knows? I might become one of those Insta-famous Influencers someday. But until then, I'll have to travel like everyone else.

In the meantime, let me finish packing and I'll update you later on what clothes ended up in my backpack/duffle bag.