Stocking anything from shirts to face masks, 24-7 convenience stores have become an indispensable part of Japanese daily life, with the sector now worth more than Sri Lanka's economy. Their secret? Constant renewal.
A staggering 1.5 billion people pass through "konbini" stores -- a Japanese abbreviation of the English word convenience -- every month, with some 55,000 outlets throughout the country, including more than 7,000 in Tokyo alone.
Competition is fierce, with two of its biggest players, Family Mart and Uny Group, announcing days ago a merger to battle market leader 7-Eleven for a bigger slice of an industry that marketing newspaper Nikkei MJ values at some 10 trillion yen ($84 billion).
That is comfortably more than the economic output of some entire nations, including Sri Lanka, Belarus and Azerbaijan.
"In our 40 years of experience, we understand that our purpose must be to offer something new all the time," explains Minoru Matsumoto, a spokesman for 7-Eleven, Japan's largest chain with 18,000 stores.
"Every time we extend what's on offer, we are creating new customers rather than taking away customers from somewhere else."
Despite being so ubiquitous, the sector has yet to show any sign of reaching saturation point, with the number of shops -- which are run on a franchise system -- rising five percent from the previous year in 2014.