He is a boy of undetermined age (although Alice mentions that hes younger than 21), and he hails from Ilias Village.

He is the current wielder of Angel Halo, a sword with the power to seal monsters.

Hes lighthearted but gullible which tends to get on Alices nerves.

Heinrich is also said to have wielded the Angel Halo, which suggests that Heinrich was also pacifistic and had the same beliefs as Luka did.

In addition, he bears his mothers Keepsake Ring, which Alice and Tamamo sense something faint from it; it has been proven that even Alice cannot sense angels as evident when she could not detect what type of creature Promestein was.

Luka also has abnormal regeneration abilities, proven through Meditation and the fact that he recovered from Granberias Vaporizing Rebellion Sword attack in merely a night instead of a month according to Alice; it is even said that Meditation was utilized by a fallen angel.

However, Luka has bursts of insightful moments, showing he isnt completely ignorant to the ways the world around him works.

For instance, he single-handedly defeated the entire armies, leaders, and champions of the insects and plants of Plansect Village, when he nearly strangles an Ilias Kreuz soldier for stealing the Garuda Egg at the Bird God Shrine, or when he threatened and attempts to kill Lazarus in Ilias Kreuz Base in Gold Port.

In almost all the rape scenes, the monster at least once claims Luka as the far most pathetic compared to other men she had raped.

Eventually, his mother died due to an illness, but before she died, she told him not to hold hatred against the village or his father and he would grow into a fine hero one day.

Alice tells him that the actions of the father do not extend to the child.

This is further proven when Alice and a few monsters, when they taste Lukas semen, describe it to have a unique taste they could get used to.

This is likely due to the Angel Halos grotesque, deterring appearance, or a homage to the RPG clich of always showing the same weapon on the characters sprite.

Despite actual age or appearance, Luka is of the age to be considered an adult in his society.

Monster Girl Quest Wikipedia