In a large bowl, mix rice krispies cereal and kakimochi. Set aside.
In a large pot or pan, melt butter on low-medium heat.
Add bag of mini marshmallows and allow to melt, still on low-medium heat.
Add soy sauce and condensed milk. Stir until everything is well mixed together and take off the heat.
Add cereal and kakimochi mixture and sprinkle furikake all over. Mix well with the marshmallow mixture.
Press into a greased 9x13" baking pan or tray. I recommend lining the pan with parchment paper to easily lift up the treats and slice them later, or they can be cut and served directly from the pan.
Let cool for 30 minutes before slicing. Serve and enjoy! Leftovers keep at room temperature in an airtight container for 3-5 days before getting stale.
Notes
You can also use a 12oz bag of large marshmallows. I just like how quickly mini marshmallows melt. The extra 2 ounces in the large marshmallows will add extra gooeyness, though, if that's what you like!
Kakimochi is also called arare or mochi crunch. They are Japanese rice crackers, and there are many different types. Feel free to use whichever ones you like, but I recommend sticking with smaller sizes or crushing them first so they fit well into the treats. If you would like to omit the kakimochi, add an extra cup (1oz) of rice krispies cereal instead.