What is the function of the OVP protection circuit (Over Voltage Protection: OVP) of NJM2386?

LDO Linear Regulators

The overvoltage protection circuit limits the output current when the input voltage exceeds a fixxed value, and protects the IC.
The detectable voltage of the overvoltage protection circuit can be determined by "Peak Output Current vs. Input Voltage" in the typical characteristics.

The electrical characteristics of NJM2386 are shown below (Fig. 1). The peak current is suppressed when the input voltage passes through about 25V. It is not detected by the potential difference between input and output.