Kana and Chiaki are known as the "BDSM couple". They're been dating for a year and operate differently then normal. Kana is the dominant in this pair. In scene 1 she wonders if their way of being a couple is right or wrong. Chiaki is not bothered by how they are. He loves it because he is a simple minded masochist. But he truly does love Kana and doesn't want to lose her. So, he comforts her in her time of need. His voice should just match his look a high school boy that sounds not too deep but not too high pitched either. Keep it simple with him.