Motoyan Papa to Hitsuji Sensei (2016)

Blurb:
In high school, studious Hitsuji had a secret crush on one of his guy friends–a friendly delinquent named Hatoyama–but never confessed. Years later, Hitsuji is a slightly anxious but responsible adult who found his calling as an elementary school teacher. One of his young students is upset with a sloppy and nonconformist dad–who turns out to be Hatoyama! When Hitsuji learns that Hatoyama is struggling to raise his son as a single parent, Hitsuji helps him out, first as a teacher and then as a friend who can teach Hatoyama how to clean his home and cook actual vegetables. As the men grow closer, some of Hitsuji’s anxieties begin to melt around the welcoming (and grateful) Hatoyama. What will become of the feelings Hitsuji used to harbor for his first love?

Source: www.anisearch.com/manga/28086