Cero is the first hollow. He will meet many people along his journey, but one thing will remain certain he will protect his people, no matter the cost, for he does not want to feel such loneliness again.
toshiro X oc
I copied this concept. kind of. Toshiro in love with a human.
Urahara had fell in love with a human who had a weird problem. Her would would leave her body with the chain attached without her control. But he couldn't just let her go to soul society. So he made a daughter from parts of him and her.
The daughter also known as his project.