It's been a while since we had a holiday chapter, also since Laika got a chance to cut loose. This holiday is Setsubun, but all you really need to know is that the main activity is someone dressing up as an oni (representing misfortune) and being chased away by tossing beans. The date isn't always Feb. 3 due to calendar calculations, but that's a usual date.
A lot of oni lore reportedly comes from encounters with foreigners, particularly Russians. This fits well with the Russian origin of some of the names, but I wasn't able to find out whether bean-throwing specifically had anything to do with foreigners.