It's mentioned by Arata that they didn't get along.
Mari is Akira's wife. When Mari said she wasn't thrill to be alone with him, he was offended. They live in Fukui.
Arata is Akira and Mari's only son. At first they were reluctant to let Arata go to college in Tokyo, since they didn't have the money. During the Individual Karuta Championship, they told him that they will give him the permission to go to Tokyo, but in episode 50, when Arata wins his match against Shinobu, Akira tries to get out of their promise, suggesting they tell him that he has to win two years in a row. Mari tells him that Arata's grandfather, Hajime Wataya, had taken out an insurance policy for Arata's education before he died. They have the money, so Arata is sent to Tokyo to study further on a karuta scholarship.