Down a Tokyo street lined with bright signs, up narrow stairs and behind a windowless door is a "snack bar" long cherished by regulars but hidden from tourists — until now.

Snack bars are cozy, retro establishments found across Japan, often crammed into small buildings and equipped with karaoke systems that echo late into the night.

They are typically run by a woman nicknamed "mama" who chats to customers while serving drinks with nibbles such as nuts, dried squid or simple cooked dishes.