As anime shows progress from season to season, there are often dramatic changes in characters. Sometimes shows shuffle between studios, sometimes actors change, and sometimes a new arc simply brings about major obstacles and growth for a given character. In the case of The Devil is a Part-Timer! a nearly nine-year gap between seasons can likely be the cause of the vast majority of changes that have been seen between the two seasons. However, unlike many of the other characters, Sadao Mao has stayed fairly true to the original vision, although he is perhaps less apologetic about it.
The Devil is a Part-Timer! follows the story of Sadao Mao, the devil, as he tries to live a new life as a human in Japan. He works at a fast food chain and lives in a tiny apartment with a few roommates. However, his previous life just can’t leave him alone. He is harassed by his old enemies, Emi Yusa and the church, as they pursue him across realities.
Visual Changes
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Sadao Mao suffered from the same visual changes as the rest of the cast. His edges were toned down, and his colors were very slightly muted. He also received a slightly more varied wardrobe. Although, the wardrobe may be less of a conscious choice on the animation department’s part and more due to the wider variety of locations. He doesn’t wear the same outfit to work as he does to the fair, or to the mall, or when he is just having casual time at home. In the first season, he really only wore his work outfit and basic t-shirts.
Personality
The devil hasn’t changed very much across the seasons, but in season two the viewers are treated to some interesting backstory moments that really deepen and round out exactly who he is. At the fair, he tells Emi the story of his childhood. The trauma that he faced and how that forced him into becoming the leader of the demons had a huge impact on Emi.
However, it also lends credibility to the idea that he might not want that role anymore. It isn’t clear exactly how old he is, although he is known to be over three centuries old. That is quite a long time to take on a kind of responsibility that he never really wanted in the first place. At the beginning of the show, he claimed that they would conquer Earth and then return to finish their conquest of Ente Isla. However, by season two he seems to be happy in his life on Earth with no intention of returning to Ente Isla.
Viewers have also gotten to see the softer sides of Sadao Mao in season two largely due to Alas Ramus. He stepped instantly into the fatherly role that the apple child assigned to him. It has been remarkable, though not surprising, how easily he took to the responsibility. He talks about her in the same way that he talked about his demonic charges back on Ente Isla, as a little soldier who must be protected, but also must fill her role in society.
But he also bends his own rules and spends money out of their frugal budget to make sure she enjoys life the way that he believes a child should. His protective instincts are also incredibly strong when it comes to her. In season one he did have some sort of protective nature, he took care of the humans in the mall collapse, but in season two he goes out of his way to protect Alas Ramus.
Overall
While other characters have had extremely dramatic arcs; Emi learning to see the world in shades of gray, Suzano changing sides altogether, Urushihara shifting from incredibly powerful villain to lazy mooch, Sadao Mao has stayed largely true to himself. His changes are just a growing comfort and confidence in exactly what he wants for himself. He is on the way to fully accepting that what he truly wants is to live a life on Earth. He doesn’t want the responsibility of an entire culture, he wants the challenge of climbing the ranks somewhere new.
It is likely that Alas Ramus will force him to stay connected to his past in a way that he won’t appreciate. However, his very clear affection for the child does imply that when she is involved he may not mind as much as he would otherwise. Sadao remaining a similar character is also important for the series because it creates a frame of reference for the other characters' changes. They are all changing around him and because of him, which gives the audience the impression that his perspective is the true, and perhaps correct, one. If he were to change his goals and personality as dramatically as they, then the throughline for the series would be buried under character drama and the show as a whole would be weakened.