Thanks to the anon who brought this old news to my attention, I dug out this video about Isayama’s parents (and kid Isayama!) on Youtube. Original TV program was aired on August 19th, 2015. Below is a translation of their interview.

Their opinions on Isayama as the author of Shingeki no Kyojin:

Father (Isayama Mitsuo): It’s not something I’ve imagined before. If speaking in our local dialect, we often say “so things like that can happen.” (T/N: It’s hard to precisely translate the sentence since he was speaking in a peripheral Hita dialect. It’s a sentence to express one’s surprise but also approval to something at the same time.)

Narrator: Isayama has enjoyed drawing since his childhood, during which time he often drew monsters.

Mother (Isayama Emi): We asked him what he wanted to do after he grew up, he said “(I want to become) a security guard at a dinosaur museum.”

Isayama told his parents that he would like to become a mangaka only after he entered a manga professional school. His parents’ comments on it:

F: I thought the probability of success (for a mangaka) can be very low… And I also had a feeling that it would be good for him to just take a normal job.

M: First of all, try it thoroughly with all your efforts. If you keep failing at it, then move on to the next thing. After all, it’s not something we as parents can decide for him.

Despite his father’s concern, Isayama created the work Shingeki no Kyojin, which has become a huge hit. How are his parents thinking about the popular work “Shingeki no Kyojin”?

F: At first I considered it “grotesque”. I made a little suggestion to him: ”Ain’t there some options such as baseball manga or soccer manga?”

M: I think it’s a quite interesting work. He has such imagination and ideas — now I start to admire his talent again.

Talking about their son’s future:

M: I think it would be good if he can keep doing what he likes while paying attention to his health.

F: If he can do some publicity service for various places in Oita prefecture or Hita city and Ooyama town, I think he himself will be happy about it as well.