Directions: Head to the back of the store where people are eating and take a left. It's right there.
Comments: TLDR: This macha gelato shop has REALLY high demand and you'll be given with a ticket to come back at a designated time. Not an option in a pinch. Long explanation: Single stall with a small sink outside. I'm not sure if it's for paying customers or not. The store is REALLY popular, so the staff will give people a ticket to come back at a later time for macha gelato. Think of it like the old Disney FastPass, if that makes sense. It was an hour later for me. If you're gonna be in Asakusa and think you'll need to go later, get a ticket and explore around. There's a lot to see here. Once your time has arrived, get some macha gelato and use the restroom.