According to AntiqueMoney.com, a division of Old Currency, LLC, Japanese pesos were issued by the Japanese government after Japan captured the Philippine Islands in 1940. At the time it was issued, the money was virtually worthless.
AntiqueMoney.com says that after Japan captured the Philippine Islands, the Japanese government used all of the Philippine and U.S. currency to fund its war effort. To replace the money that it took, the Japanese government issued centavos and pesos. The money was considered so worthless that it was usually just found lying around the streets. The only notes of value to collectors are the 100-peso notes.