Not sure what is on the JP menu, but menu-wise here if you order a Double Cheeseburger it's two patties and two slices of cheese, while the McDouble will get you the two patties and one slice of cheese, but it is slightly cheaper.
It might seem silly for the difference, but when you're paying 54 cents for an extra slice of cheese, for some that does add up over time.
For how much art this series has on this site, I find it weird there's only over 160 pieces with Touya. And even less so with Yukito. Yue isn't much better.