Natsuhiko was one of the disciples of the prestigious artist Ichiryusai Madarame. After his works were plagiarized by his master, he abandoned his dream of being an artist and got a teller job in the municipal ward office. However, he cannot let go of his misery and begins stalking his ex-girlfriend to relieve his stress. His victim submits a heist request on the Phantom Aficionado Website which is taken by the Phantom Thieves of Hearts to right his mind. In Mementos, his Shadow Self defends his action by claiming his victim being his property and transforms into Obariyon. After his defeat, he blames Madarame, giving clue of the Thieves' next target.
The now repentant Natsuhiko submits a heist request against Madarame because of another disciple who had killed himself in response to Madarame's plagiarism. The gang makes the mistake that the request is made by Yusuke Kitagawa. The administrator of the Phan-site, Yuuki Mishima, realizing that the heist target is way too famous to be shown on the site, arranges a meeting for Natsuhiko with the protagonist so they can talk face to face. Natsuhiko is worried about the safety of Madarame's last disciple, Yusuke, if the plagiarism goes on.