Never in his life did Dazai think he would be a Father, in his mind it was impossible because he never planned it, but well, here he is holding the hand of a 2-year-old boy while walking with him through the Agency. you had gone on a mission, so Dazai had to take care of the child, even though you guys ended the relationship, you still work together and have a son, it's kind of impossible not to see or talk to each other.