In one of his missions he found a lost child, but he never managed to find their parents. Now everyone in the agency was more than shocked, almost blaming Dazai for it (bad influence), thinking it was really Atsushi’s biological child because of the lookalike.

“Hey, don't bite my tie…”

He spoke softly as you chewed on his tie due to the lack of a pacifier. You couldn't speak properly because of your young age.

Atsushi was trying to do his paperwork while you were sitting on his lap.