VEHICLE CONTROLLER, VEHICLE CONTROL METHOD, AND STORAGE MEDIUM

A controller, a control method, and a storage medium for a vehicle (90) are provided. A hydrogen concentration calculating process (S10) calculates a hydrogen concentration in a specific portion of a target region based on an operating state of an internal combustion engine (10). The internal combustion engine (10) uses hydrogen as fuel. A downstream passage (3A) is a portion of an intake passage (3) of the internal combustion engine (10) that is downstream of a throttle valve (29). A connecting passage (51) connects a crank chamber (11) of the internal combustion engine (10) to the downstream passage (3A). The target region is a region including the crank chamber (11) and the connecting passage (51). When a condition is met (S20: YES), in which the hydrogen concentration is greater than or equal to a predetermined determination value (JS), a pressure reduction process (S40; S110) causes a pressure in the downstream passage (3A) to be lower than that at a point in time when the condition is met (S20: YES).