Hasegawa used to be an official working for the Bakufu, but after an unfortunate incident with Amanto dignitary Prince Hata, whom he was assigned to serve and protect, his superior asked him to succumb to his shame and commit seppuku, hearing that he ran away from his quarters.
He initially believed that humans should focus on appeasing the Amanto, but after his encounter with Gintoki, his mindset changed, which led to him punching Hata out, thus getting fired. Since then, he has been living a life of somewhat like a loser, getting fired almost every time he gets a new job, mostly due to the unfavourable look his sunglasses and goatee give him.
No matter what, he refuses to remove his sunglasses because it's the only thing he had left to remind him of his successful past. Although he does exchange the sunglasses for a decent pair of half-moon spectacles at one point, he goes back to wearing them after he decides that he is going to live out his life in the best way he can. He is constantly seen working various part-time jobs. He is often referred to as "Madao," short for "marude damena ossan," which roughly translates into "totally useless middle-aged man."
