Throughout his entire upbringing, Riku Tachibana has been under the care of his grandfather. The elderly man had a peculiar penchant for employing odd hand gestures, an idiosyncrasy that has inadvertently affected Riku’s behavior. He now casually imitates the same gestures, to the amusement of his fellow students. Nonetheless, Riku’s perception of the unusual practice abruptly transitions when he comprehends its concealed meaning. This newfound realization could determine Riku’s survival in dire situations.