He is a student of Class 2-3 in Midorigaoka Academy and a member of the Student Council. Kosaka is a smart boy who is confident in his skills and brains. He is good at planning and organization, however his plans are, as stated by Hanabusa Miyabi, "only good on paper". He will panic when presented with a problem he did not anticipate and be unable to solve it due to his rigid and inflexible personality. He is socially awkward but does not have trouble speaking to others. Instead, he does not understand others feelings to him that well, unless they are clearly said. For this reason, Kosaka has failed on all of the dates that he has been on, since none of the girls specified that they were dates.