Research has been conducted on attaching a robotic arm to a human body and using it as a supernumerary limb. However, it remains unclear what type of behaviors contribute to the induction of embodiment in a supernumerary limb. In this study, we created a virtual environment where we could observe behaviors that contribute to the embodiment of avatars and tools, such as "looking at one's own body in a mirror,""moving the supernumerary limb quickly and accurately,"and "paying constant attention to the supernumerary limb,"and verified whether these behaviors are also effective in inducing the embodiment of the supernumerary limb. After spending 40 min in a behavior observation space, the left hand, the side with the supernumerary limb, was used significantly less frequently. In addition to these behaviors, "self-touching,""transferring objects between their own hand and the supernumerary limb,"and "whole-body movement"were also observed. The observations suggest that these behaviors may change the awareness of the supernumerary limb and contribute to the improvement of its embodiment.