Maybe magic of department store. You put the same thing in Tokyu Store and the same in depaato, make sure to overprice it. People will buy from depaato. Probably for a gift. It just works like that in Japan.

Plenty of KitKats is in my local Tokyu Store - no one is buying them. I never saw anyone in my office eating KitKat even once. They eat plenty of other sweets, often local. Also no one ever brought it as a travel gift (omiyage.)