Reduce the weight you carry with you by avoiding carrying a lot of coins. Buy a PASMO card. With the swipe of your PASMO card, you can buy drinks from a vending machine without having to dig through your change or even having to carry it to begin with. The downside to this is that you may not end up using any remaining credit on your card. I am still trying to figure out whether I want to bother with this or just give my PASMO card to someone else who may be traveling to Japan. I charged mine with $20 worth of credit and only used about $5.00 worth on a three-day trip traveling solo. The Suica card works similarly.
The ultimate in minimalist travel in Japan is to try out one of the capsule hotels. First Cabin is a chain that provides three sizes of cabins/capsules. The smallest, least expensive one has very low ceilings and runs about 4500 yen. Although I am not tall, I wanted something I could stand up in if I wanted to. I chose the midsize one for about 5500 yen. The largest size has a bedside table and a narrow strip of carpet along the side of the mattress, just wide enough for the table. As of July 2018, those cost about 6500 yen.
Although the screen door to the cabin does not close all the way in accordance with Japanese laws, it was very safe. Two floors are reserved for women only and two for men. To enter your floor, you must carry your badge with you to swipe the doors open. (Remember to bring your card with you in the middle of the night if you have to go to the restroom. It comes on a lanyard, which makes carrying it with you easy.)