I hope this reply is not too late. I e-mailed for the reservation. We were there in March 2017 and there was a line of people with reservations to get in so I would suggest try again. It's a super unique experience- my teen daughters loved it as much as they loved the deer in Nara.

I have a 2.5 year old nephew and I would not take him. the whole experience is to hold the hedgehog but they are sharp to touch. plus the space is small and tight, so unless your child can sit still for an hr, I think your child might lose interest and would want to walk around. I suggest the bunny cafe above 1 floor. The rabbit is much more calm, allowing you and your child to pet it easily. Ben

Yes, that's true. I would reccomned booking an appointment online and not go in as a walk-in. That's what we did. The hedgehogs need downtime and I noticed they were quite sweet and perky for us, but even after 1 hour they faded. So I think the best slot would be right when it opens @ 12 noon. I'd go back again, but am having second thoughts about the kindness of animals cafes(to the animals).