Ishida has lived a 'lone wolf' life after being blamed for the sole bullying of Nishimiya Shouko during elementary school. Six years later after meeting Nishimiya again and befriending her, he starts to gather new friends together, along with old ones he had during middle school. Despite the changes in his life, Ishida still struggles to make up for what he did in the old days.

During grade school, Ishida loved to go on self-imposed adventures and played a lot, in what he described as a battle against "boredom". He always played pranks with living things or other kids. After Nishimiya transferred to their class, Ishida became more devious as he always mocked Nishimiya, which resulted in him receiving scoldings from his teachers often. After he became the scapegoat for the bullying of Nishimiya, Ishida was isolated from everyone and became a very introverted individual. He was deeply filled with regret for all the things he did to Nishimiya, and started to contempt others. He also slowly grew to hate everyone and see them as "pretenders", such as Mashiba (who he thinks brown hair doesn't suit him), or Kawai Miki (calling her a hypocrite though initially it was not a complete lie). Above all, Ishida hated himself for having bad thoughts about everyone else. After reuniting with Nishimiya in high school, Ishida starts to gain friends, hang out and laugh more. Throughout this time, he has the objective to give Nishimiya back the happiness he once took and helps her find the old friends she once had. Even with these acts of atonement, Ishida still struggles in moving on when he remembers his past mistakes and the isolation that followed. Despite getting mad at someone, later on, Ishida usually is the first one to apologize with his actions and thinks he doesn't have the right to do so. He admitted to Nagatsuka Tomohiro that he became the way he is now because of Nishimiya.