An information processing device includes a memory; and a processor that executes a program stored in the memory, wherein the processor executes an operation including: receiving first stream data and second stream data that each include a piece of reception data representing a set of a key and a numerical value, when detecting, from the second stream data, a piece of reception data with the same key as a key of a piece of reception data of the first stream data, obtaining a processing result by adding together numerical values of the pieces of reception data that have the same key, and storing the processing result in the memory.