1. An information processing apparatus, comprising: circuitry to: detect positions of a plurality of users existing in a detection target area; calculate a plurality of feature quantities representing a relation between the positions of the users detected by the detecting and a projection plane on which a projection image is projected; and determine display control processing for the projection image depending on the feature quantities calculated by the calculating, wherein: the calculating calculates, as the feature quantities, directions of the positions of the users detected by the detecting, relative to the projection plane, based on the positions of the users in the detection target area, the determining determines the display control processing for the projection image depending on the directions of the positions of the users relative to the projection plane that are calculated by the calculating, the calculating calculates, as the feature quantities, a position of concentrated area where the users detected by the detecting exist in a concentrated manner, relative to the projection plane, based on the positions of the users in the detection target area, the determining determines the display control processing for the projection image depending on the position of the concentrated area relative to the projection plane that are calculated by the calculating, the calculating calculates, when the concentrated area is reduced and a position of a user is detected outside the concentrated area but in the detection target area, a distance between the position of the user and the projection plane, as the feature quantity, and the determining determines the display control processing for enlarging the projection image when the distance calculated by the calculating is equal to or smaller than a given distance.