This is pretty rough idea of what happened... I didn't want to pressure Kuro to tell me details since it hurts him a lot to think about what Lotus did.
(This was after Maia made Lotus sterile, back when Nao was Lillian and she was still under Lotus's control.) Since Lotus had Lillian, she had a good heir to her throne. But she figured she could use Lillian for other means and she did have a way to make one more child. This was around the time when she didn't have Izzamer captured yet but Shanks was still available for a bit, so Kuro is a full brother to Noemi, Nishi, and Nastu. Lotus eventually came up with a baby boy she named Ozzie. She realized the boy was very trusting and decided to use this to her advantage. She would be using him to lead the people in the Kingdom of Darkness for her, right? The colder and meaner the leader they had, the more like perfect little soldiers they would be to her usage. So she waited until little Ozzie was six years old to turn him into what she needed. Those six years he had growing up she was the best mother to him, loving and trusting and not suspicious of the malicious activity she engaged in. But when she experimented on Ozzie, it went all wrong. She turned him into a raven boy with basic light with a few aging spells to make him older, quite simple compared to her other elaborate creations... But when Ozzie stopped crying, his expression was that of what Lotus wanted; pure, rage-ful hate. Little did Lotus know that Ozzie was smarter then she thought. He planned to get back at her for betraying him so horribly. He allowed Lotus to take him to the Kingdom of Darkness where he began wrecking havoc and destroying all that he could with his light powers. Lotus soon found her mistake and marked him an ultimate failure, manifesting the light powers out of him and scarring him deeply, mentally and psychically. During this battle was when Kuro received the scars over the bridge of his nose and over his right eye, as well as "Exp. 501606UF" branded into his neck. (5=The number of children Lotus had, 0= space, 16= the age he was after the aging spells, 0= space, 6= the age he was before the spells, UF= Ultimate failure.) After the battle Lotus let Ozzie run off into the woods
to die. But little did she know that he had survived. A man who lived in the woods with a wife who could not give him any children took Ozzie in and hid him, and also gave him shadow powers which had previously been kept in the family sword. By now, Ozzie was sickened with the thought of his mother and changed his name to Narikuro, meaning "dark clarity" in Japanese. He decided Kuro would be his nickname. Kuro lived with the man for a very long time. The man's wife died, and Kuro was still there. But at age 26, the man fell ill with a terrible sickness and he too, died. Kuro had been like a son to them, and now he was alone again. Kuro buried his foster father next to his wife and lived in the house until I discovered him yesterday, about two years since the man died. Apparently nobody in the kingdom wanted to take in Kuro either, and he just became a legend in the woods.... The raven boy. Now Kuro lives with the memory of Lotus through the word "Mama" carved in uppercase letters on his chest, a scar he inflicted on himself and made worse over the years. When he remembers the pain of her betrayal, he goes over the letters again.