Who is Oko from Changes: A Love Story and what is their importance?

Oko is Esi's first husband and Ogyaanowa's father. He is embarassed that Esi seems to love her job more than him, and an argument between the couple leads to Oko raping Esi. As a result, Esi divorces Oko. He moves to the country when he is promoted to a higher position with the school there, but he cannot accept the fact that Esi has left him. When he encounters Ali at Esi's bungalow, he fights his ex-wife's new husband. He somewhat holds Ogyaanowa over Esi's head, but Esi never returns to Oko.