Kamiki plays the lead character Kiriyama Rei, a 17-year-old professional shogi player who made his debut during junior high which was extremely rare. He lives alone at a suburb town in Tokyo as his parents and younger sister died during a traffic accident when he was young. While coping with the loneliness in his life, Rei aims to become a top-class shogi player. One day, Rei comes to know three sisters from the Kawamoto family i.e. Akari, Hinata and Momo which offers him much-needed warmth in his life as he grapples with the struggles in the competitive shogi world.
When news of the movie adaptation first came out, Kamiki was one of those whose names were suggested as most suitable to play the lead character. Kamiki himself also expressed his joy when offered the role as he is a fan of the manga which is widely popular. Despite feeling the pressure, he promised to try to convey the heartwarming theme as projected in the original manga. Ohtomo who last worked with Kamiki in the Rurouni movies, expressed excitement at seeing how the latter has grown in the last two years and is looking forward to see how he will portray Rei this time. Meanwhile, the original manga's author also praised Kamiki for being a guy who feels as if there is a lion residing inside of him and is very happy about him playing the lead character.