They're divorced. Taka did not see his father growing up that's why he doesnt know and his parents kept it that way. Maybe so Taka wouldn't be confused as he's still a toddler.
Although Taka's Mom was his Dad's ex-student, they had kids when they were already Colleagues, so she was already an adult then. They're just maintaining professionalism inside the school now, even though they're Divorced.
I see. Thank you.
But he could still show up for his kids and be there. They are in the same place every weekday.
also with a family register (koseki), I think that is why they all have the mother's maiden name
So why does he not live with them and when did this happen? Was it when Hayato was little? How did they create Taka if the papa is hiding in the shadows? I hope we get a deep dive on this soon. Maybe the dad thinks it is unprofessional since he did end up having kids with an ex-stufent who is now also working in the same place as him? IDK.