[Accessible Japan]

Hello,

According to the airport website:

There are temporary storage facilities for carry-on baggage at the northern and southern ends of the 1st and 4Fs. The northern counters are operated by Kansai Airport Baggage Service, and the southern counters are operated by JAL ABC.
It is 620 yen to leave a suitcase for one day, 360 yen for a Boston bag, 1,030 yen to leave a coat for 4 days or less (from the 5th day, 210 yen is added per day), and large items such as surfboards may be left for 1,030 yen a day.

https://www.kansai-airport.or.jp/en/service/delivery/01.html

So, it looks like it would be 620 yen per day for your suitcase…

Some bigger train stations offer luggage storage, but unlike the airport, they won’t let you leave it for multiple days.

I guess you’ll need to look at how long you will leave it and then see which is cheaper.

Japan isn’t cheap!