He is a rounded old man who wears glasses. When he was a child, he was thin and had a shaven head with a gap in his teeth.
When he was a child, he had a mischievous personality present in some kids. As he became an old man, he became a serious person, but when around Nakai Chitose, he is soft.
When he grew into an adult, he became a principal of a middle school. And made Chitose's dream come true, to study like a normal person does. It is unknown that he still has feelings to her like his childhood.
Tsutomu is seen talking to Nakai in the middle school about the past.
She is the zashiki-warasi of Yuragi-sou. When Tsutomu was a child, he would often play with her and even once asked her to marry him. In the present, he is the principal of the middle school that Chitose attends.