He comes from a small town. He struggled in his teens because of his sexuality. As a child, he always felt affection towards Masaki, who was the best friend of his older brother Kunihiro Morinaga.

In high school he fell in love with Masaki and engages in a relationship with him, but after almost one year of secret relation, they were discovered by Kunihiro, and both are despised by him. Masaki doesn't bear the words of scorn from Kunihiro. He confesses to Tetsuhiro that he was in love with Kunihiro. After some time, Masaki attempts suicide. The attempt fails. Morinaga repeatedly tries to see Masaki, but isn't allowed. Hence, the degradation for being gay from the family, and they accuse him of dragging Masaki into a relationship with him. After the incident, he does not return to see Masaki again. 

After graduating from high school, he moves to Nagoya to continue his studies; and thus, leaves the town and then applies to the University of Nagoya, the Department of Science and Agriculture. In the winter of his second year, he falls in love at first sight with Souchi Tatsumi, an upperclassman who is feared in college for his tyrannical personality. After several failed attempts, he manages to strike up a conversation with him, then becomes his assistant.

He usually frequents a gay bar where his friend Hiroto works.