A navigation system includes a detector configured to detect a situation in a movable object, a determiner configured to determine a degree of activity of conversation in the movable object on the basis of a detection result by the detector, a movement plan setter configured to set a movement plan on the basis of setting information which is set by a user, and to change at least part of the set movement plan on the basis of a determination result by the determiner, and a navigator configured to navigate the movable object on the basis of the movement plan which is set or changed by the movement plan setter.