1. An image processing device comprising: a memory; and a processor, coupled to the memory, configured to: acquire an image which includes a first region and a second region of a user, the first region corresponding to a dorsum of a hand of the user and a portion from a second joint to a third joint of a finger of the hand, the second region corresponding to a region from a fingertip to the second joint of the finger of the hand; detect, from a plurality of candidate areas for the first region and the second region included in the image, a first candidate area corresponding to the first region based on a predetermined image feature of the first region and based on an image feature corresponding to wrinkles of skin on a first joint and the second joint of the finger extracted from the image, the predetermined image feature including at least a statistic of pixel values of the first region; determine parallel line segments included in outer edges of the first candidate area; and select a second candidate area corresponding to the second region from the plurality of candidate areas based on the parallel line segments.