MUJI is a popular clothing, interior, knick-knack store all over Japan (and in some countries abroad).
I use the MUJI app, called MUJI passport, to keep track of shopping points.
You can also check-in to MUJI stores (once a day) and get 10 points (equivalent to 10 yen) per check-in as long as you are no farther than 600 meters (0.3 miles) away.
For the year, as your shopping points and check-ins accumulate they give you shopping coupon when you reach a certain amount, the higher the amount of points, the higher the amount of the shopping coupon.
When we take long train rides, I check-in at various MUJI shops when we stop at a station that has a MUJI shop nearby, if I remember to...
Recently they changed the type of check-in stamps we receive.
The stamps before were kind of boring, if I remember correctly, just a round circle that said "MUJI check-in".
Now, the stamps are fun...representing the areas that the shops are located.
For example, Osaka's stamp is of Tsutenkaku (the tower that is a landmark of Osaka and kinda looks like the Eiffel Tower).
Since MUJI also has shops abroad, I hope to be able to collect some check-in stamps, (if and) when we travel international.