Fukubukuro (Japanese: lucky bag, mystery bag) is a Japanese oshogatsu (first days of the new year)  custom where merchants make grab bags filled with unknown random contents and sell them for a substantial discount, usually 60% or more of the list price of the items contained within. Fukubukuro was invented by Ginza Matsuya Department Store in late Meiji period and has since spread to most retailers. These bags are usually snapped up quickly by eager customers, with some stores having long lines snake around city blocks hours before the store opens on first or second January.
Akiba shops sell their Bukubuko too. Usually the biggest shops had the most interesting ones, but this year Akibao, Super Potato and other "underground“ shops displayed the most interesting Fukubukuro!  This year even adult shops like M's Entertainment or Love Mercy got their own bags full of adult toys!