In an apparatus, a storage stores therein first identification data prepared for each of target objects including a specified target object and second identification data prepared for each of the target objects. The first identification data for each of the target objects is determined based on a first feature pattern of a corresponding one of the target objects. The second identification data for each of the target objects is determined based on a second feature pattern indicative of a surrounding environment around a corresponding one of the target objects. An identifier obtains a degree of similarity of the feature of the candidate data with respect to the specified target object according to the first identification data and the second identification data prepared for the specified target object. The identifier identifies, according to the obtained degree of similarity, whether the specified target object is in the environmental data.