An image capturing system including an image capturing apparatus (110a to 110d) comprising a first storing means, a first processing means,a determination means, and a mounting mechanism for SD card insertion and removal, and an auxiliary processing apparatus (100a to 100d) that can be attached to and detached from the mounting mechanism, comprising a second storing means and a second processing means, wherein the first storing means is configured to store, in advance, a first image and a first signal information that is an expected value to be obtained when the second processing means executes a predetermined processing on the first image; the first processing means is configured to send the first image to the second storing means that is different from the first storing means in a case where the auxiliary processing apparatus (100a to 100d) is attached to the mounting mechanism of the image capturing apparatus (110a to 110d); the second processing means is configured to process the first image stored in the second storing means according to the predetermined processing in a case where the auxiliary processing apparatus (100a to 100d) is attached to the mounting mechanism of the image capturing apparatus (110a to 110d); and the determination means is configured to determine whether or not at least one of the second processing means and the second storing means is anomalous based on whether the first signal information matches second signal information obtained by the second processing means processing the first image in a case where the auxiliary processing apparatus (100a to 100d) is attached to the mounting mechanism of the image capturing apparatus (110a to 110d). an image capturing apparatus (110a to 110d) comprising a first storing means, a first processing means,a determination means, and a mounting mechanism for SD card insertion and removal, and an auxiliary processing apparatus (100a to 100d) that can be attached to and detached from the mounting mechanism, comprising a second storing means and a second processing means, wherein the first storing means is configured to store, in advance, a first image and a first signal information that is an expected value to be obtained when the second processing means executes a predetermined processing on the first image; the first processing means is configured to send the first image to the second storing means that is different from the first storing means in a case where the auxiliary processing apparatus (100a to 100d) is attached to the mounting mechanism of the image capturing apparatus (110a to 110d); the second processing means is configured to process the first image stored in the second storing means according to the predetermined processing in a case where the auxiliary processing apparatus (100a to 100d) is attached to the mounting mechanism of the image capturing apparatus (110a to 110d); and the determination means is configured to determine whether or not at least one of the second processing means and the second storing means is anomalous based on whether the first signal information matches second signal information obtained by the second processing means processing the first image in a case where the auxiliary processing apparatus (100a to 100d) is attached to the mounting mechanism of the image capturing apparatus (110a to 110d).