Childhood[]
As a child, being born into a rich noble wealthy family was considered as a great prestige and honour to him, which reflects in the way and manner in which he considers himself to be pure and virtuous, referring himself to as "The Holy Angel Akoya" in the manga when quizzed by the then student council second year's, Kinshiro and Arima. He seems to have a dislike for his last name, "Gero" which translates to either a frog's mimicking or its literal meaning (to puke) along with jokes that are made from the word "to run away" (niigero), all of which have led his classmates to make fun of him, as his name contrasts his appearance.
This is possibly one of the reasons or incidents which have shaped his behavior to what he is now, and the reason as to why he despises the sight of a thing that is not pretty in appearance.