Shiroishi is Kazuko's classmate, and the boyfriend of Terumi, the girl who died as a precursor to the main story. He is grieving, and suffering from visits from Terumi's "ghost". The voice I envision for this character is emotionally exhausted, somewhat bitter, and stubborn. Eventually, Shiroishi falls victim to the hanging balloons himself in attempt to reach out to Terumi. This role involves crying.