VEHICLE CONTROLLER, VEHICLE CONTROL METHOD, AND STORAGE MEDIUM

A hydrogen concentration calculating process calculates a hydrogen concentration in a specific portion of a target region based on an operating state of an internal combustion engine. The internal combustion engine uses hydrogen as fuel. A downstream passage is a portion of an intake passage of the internal combustion engine that is downstream of a throttle valve. A connecting passage connects a crank chamber of the internal combustion engine to the downstream passage. The target region is a region including the crank chamber and the connecting passage. When a condition is met, in which the hydrogen concentration is greater than or equal to a predetermined determination value, a pressure reduction process causes a pressure in the downstream passage to be lower than that at a point in time when the condition is met.