We want to make our own Cup of Noodle and it looks like online that you have to get your tickets the day you visit the museum. Does anyone know how early you need to get there before the tickets sell out?
I would recommend going early in the morning if you are going during a weekend. Generally during weekdays are not so full so you can take your time.
But the best recommendation is to go in the morning, about 10am get your reservation and enjoy Yokohama until your time.
You can also book at Loppi ticket machines in the Lawson Kombinis (but it will be in Japanese, you should get someone's help if you can't).
If you decide to go to yokohama and enjoy other things, I find these some pretty great itineraries with many options to have fun there:
In any case, good choice, It's a lot of fun!