Controller for internal combustion engine

A controller for an internal combustion engine, the internal combustion engine being mounted on a vehicle, the controller comprising processing circuitry, wherein

• the processing circuitry is configured to execute:
• a fuel injection process of executing fuel injection by a fuel injection valve of the internal combustion engine on condition that a start switch of the internal combustion engine has been turned on;
• a leakage determination process of determining whether there is fuel leakage from a fuel supply system of the internal combustion engine on condition that the start switch has been turned on;
• and
• a start estimation process of estimating whether there is a possibility of a start operation before the start switch is turned on, the possibility of a start operation refers to likelihood that the start switch will be turned on,
• the processing circuitry is configured not to execute the fuel injection through the fuel injection process if the leakage determination process has not been completed in a case in which the start switch has already been turned on, and
• the processing circuitry is configured to start the leakage determination process when the start estimation process estimates that there is the possibility of a start operation even if the start switch is not turned on.