He had been hunted down by the Mexican Mafia Gang, and found himself unconscious in an alleyway, vaguely aware of someone taking care of him.
When he woke up, he realized that he had been brought to the orphanage by Bai Xinxin.
Those who were after him found his whereabouts; in order to kill him, they detonated a bomb.
He was severely injured at the time and incapable of dodging the explosion. If Bai Xinxin hadn't lunged forward and pushed him away, he would have died then and there. The orphanage lost 128 lives in that bombing, and Bai Xinxin was seriously injured and left with incurable sequelae.
What he owed Bai Xinxin was not just the debt of life but also the guilt for the loss of those 128 vibrant lives.
And Bai Xinxin's existence was a constant reminder. Those lost lives died because of him.
The burden of responsibility was too heavy. Therefore, when Bai Xinxin confessed her love for him, he agreed without hesitation.
