Haruto Mizushima is a childhood friend of Sousuke and the cousin of Arata. At the same time he attends Seiso Academy and is a member of the Orchestra Club as a Cellist. He is a first year student thus his shirt is embossed with the red colour of the first year students. It should be noted that unlike in the first Kiniro no Corda year colour specialization has changed: red for first years, green for second years and blue for third years.