ANOMALY DETECTION DEVICE FOR INTERNAL COMBUSTION ENGINE, ANOMALY DETECTION METHOD FOR INTERNAL COMBUSTION ENGINE, AND STORAGE MEDIUM

A first pressure sensor is disposed in a first fuel system between a first shutoff valve and a second shutoff valve. A second pressure sensor is disposed in a second fuel system between the second shutoff valve and a fuel injection valve. A determination process determines a leakage anomaly in the first fuel system or the second fuel system based on a first magnitude relationship or a second magnitude relationship. The first magnitude relationship is a relationship between a detection value of the first pressure sensor in a state in which the first fuel system is filled with gaseous fuel and a first threshold value. The second magnitude relationship is a relationship between a detection value of the second pressure sensor in a state in which the second fuel system is filled with gaseous fuel and a second threshold value.