Onigiri is a great snack to meal prep and take on the go. If you want to enjoy it in the future, though, make sure you know how to properly store it.

For instance, “Kaitaku onigiri” (Pioneers’ onigiri) had umeboshi (salted pickled plum) for its filling, a sprinkling of salt and sesame on the rice, and was slightly grilled before it was ...