Lucifer

Lucifer is a fallen angel and one of the Demon King's generals. After his defeat at the hands of Hero Emilia, he was secretly rescued by Olba Meyer, who promised to return Lucifer to heaven if they became allies in defeating the Demon Lord. After being defeated by the Demon Lord, Urushihara moved in with Sadao Maou and Ashiya.

Lucifer is shown to be cunning and sneaky as well as a childish, preferring to surf the internet and play video games rather than help Ashiya with the housework. Due to his attitude, everyone tends to treat him lightly and pay no mind to many of his protests at being excluded from things. Lucifer is also self-proclaimed socially awkward, lazy to an extent, and has a short temper. However, it seems he has hidden feelings beneath his seemingly irresponsible and carefree attitude, and shows his serious side from time to time. To his irritation, Lucifer is usually referred to as a hikikomori even when among company.

(Source: Hataraku Maou-sama Wikia, edited)