Roundabout, The Shortest Distance Is Round (2019)

Haruto is a freshman and a loner high school student until the arrival of the new teacher Aoyama. Aoyama cares for Haruto and starts to exchange letters with him, as something more grows inside both of them. But one night, an unexpected kiss ends their beautiful relationship. Three years later, Haruto has become a male prostitute in order to pay back his debts, when he reunites with Aoyama by chance.