You Can't Love Back An Immortal

Athanasios Thanasis is a immortal. He have powers like other immortals too. Immortals don't have any emotions. They can't fall in love with mortals.
Until one day he heard a girl's voice. That sweet voice coming from the earth. That voice changed his entire life. As a immortal you can't fall in love with a mortal. He don't know that falling in love can be a sin. He let his heart rule his body. Higher immortals gave him a tough punishment. Punishment that he'll die and born for a longest time. He lived in the earth for a decades, a centuries or maybe forever. He can only die if he found the one destined to kill him. But days past he can't still find the one.
He realized that this punishment is a blessing disguise, he met the girl that owns the sweet voice he heard when he's still in the Agartha, A legendary city at the Earth's core. But all things broke into pieces. why?