The following photos are from a store that sells miscellaneous goods for the home: gardening suppllies, cleaning supplies, heaters, etc. etc. etc.
A person can buy plant leaves which can then be made into New Year’s decorations. (Unlike many other Asian countries, Japan celebrates New Year on January first nowadays. NOT in February.)
The decorations are not kept long after the New Year’s celebrations are over. They are usually brought to a shrine and burned, or in my Obaasan’s more traditional area, the neighborhood has a bonfire and people throw in the decorations, along with anything else of sentimental value they want to dispose of. (I know this because my MIL took a stuffed toy that the cat often chewed on. Because it was sentimental, she threw it in the bonfire, rather than the garbage.)