Hapuku had been in charge of Mikara while his mother Jamie Reti was in the house feeding and bathing her elder son. However, Hapuku spent most of his time playing a PlayStation game. It wasn't until a parole hearing in 2014 that Hapuku acknowledged that he hit Mikara once in the abdomen leading to his death.
Yesterday, Mr Te Aho said he still struggled to make sense of Mikara's death.
He suddenly felt the pain that he had only watched other people express on the news.
"Every case of child abuse I know affects me deeply as I know what the parents are going through."
He said he felt he had an obligation to speak out for all the children.
"I felt I needed to be here today to support not only Moko but my own son who passed away, as well as all the other children. For all the parents and victims out there who might not be able to be at something like this as it's too hard-out or raw for them, I'm here for all of us and my whole whanau," he said.
Despite the strength he showed speaking out, Mr Te Aho said it was "really hard".
"It's something that never really gets any better - it never changes, you just find better ways to get on in life. It doesn't matter how many times you talk about it you still feel that same hurt you felt that day ... all the feelings come flooding back."
Mr Te Aho said it was "devastating" to see the "growing epidemic" of child abuse around the country. He felt betrayed by the justice system and said he would like a minimum sentence for all child abusers. As he stepped back into the crowd he picked up his young daughter and gave her a big cuddle.