Asura and Han Sen's mother had some kind of entwined fate that they could not be freed from. The Luo family had the Shura's Falsified-Sky Sutra, which made the Luo family and Shura's Jade Shura fall into a generation of loving and killing.
During Luo Lan's generation, Han Sen's mother wanted to prevent their heirs from falling into the same cycle. Thus, they hid their names in the hopes that Han Sen could lead a normal life. Unfortunately, it did not work. Han Sen received the Asura Sutra by accident. He had also found Zero, who had a strong connection with the Shura.
The little sister, Han Yan, practiced the Luo family's Falsified-Sky Sutra. Ever since then, Han Sen's family and the Shura, or the Asura King who created the Shura, had a fate that always caused them to be coiled around each other in some capacity.
After Han Sen entered the geno universe, he believed the Demons might have been connected to the Shura, but he lacked proof for the allegation.