Humans are a race of people that inhabit the Human World named after them, and frequently mentioned in the Mairimashita! Iruma-kun series.
Humans are people who live fairly mundane lives. Compared to demons their strength and power is far lower than the latter as they are unable to use Magic and are physically much frailer. The most well known human is the titular Iruma Suzuki who is a 14 year old boy who was sold by his parents to Lord Sullivan who ended up adopting Iruma as his grandson.
Connection to Demons
Although both the Human World and the Demon World are mostly separated with each one largely unaware of the other, several stories narrate humans forging contracts with Demons for power in the past. However, at present time, no such practice is done and many Demons believe that Humans are actually a myth and do not exist, which is expected as neither side has any real interaction at all.
This puts the ancient stories into question as to whether there was any truth to them or not. Ironically, the Babylus Demon School has its signature hymn declare that Humans exist purely to be food of the Demons, although in actual practice many Demons are puzzled as to why given they have never met any human before. However, as seen when Naberius Kalego became Iruma's familiar following a summoning ritual, largely as a result of Iruma's nature, it gives credence to these very stories.
However, due to Lord Sullivan warning Iruma to not let his identity as a Human be known, going as far as imbuing him with scent that masks Iruma's Human nature, it is thus hinted that Demons can, indeed, if given the chance eat Humans in their proximity. This also hints at a rather antagonistic relationship between the two races, if any such did indeed occur in the past.
As seen with Iruma himself and his circle of friends, it is made evident that the two races can indeed coexist peacefully, although largely a result of Iruma's nature not being made public.