Rain is an interesting thing, because the number of bikers in Tokyo goes down maybe by 60% or more the second it rains. I kinda avoid as well.

Nothing Tokyo specific about that, biking in the rain is dangerous and generally sucky. I have good all weather gear, but I still end up with wet shoes/socks and muddy spray up my back and legs (yes, I have a mudguard, but it's not 100% effective).