A locking and unlocking system includes a controller. The controller is configured to acquire a state of locking and unlocking of a vehicle that is locked and unlocked based on locking and unlocking instruction information acquired from a portable terminal, and send a notification to a first device associated with the vehicle, when the vehicle is not locked during a period of time from when the vehicle is unlocked based on the locking and unlocking instruction information acquired from the portable terminal until a first timing.