Brandon was an adult when he found out that he had been adopted. It came as quite a shock. He spent his whole life thinking that the world was one way when in fact there was another layer to it. As much as he loved and cherished his adoptive parents, he wanted to find his biological mother. He contacted the adoption agency, but her information wasn't listed. He had a few clues and followed them, but they led to one dead-end after another. Brandon became obsessed. Sparing no expense, he employed a world-class detective. After many months of searching, the renowned detective came up empty-handed. Brandon never quit, though. He spent years and piles of money scouring the world for clues to his birth mother's identity. Finally, his efforts paid off. He discovered that she was living right down the street from his house, just around the corner.

Which type of irony is used?
Explain your answer: