Absolute Sword Sense Description: After being given up on by his family because his dantian was destroyed, Soh Woonhwi was kidnapped by the Blood Cult and lived as a third-rate spy. One day, he died while being used to find a legendary sword immortal’s secret records. However, he returned to the day he was kidnapped ten years ago and obtained a mysterious ability that allowed him to hear the voice of swords. Recent Thought: Dang, the most recent chapter, 118, really makes me want to see how he’s related to the blood demon.
I'm betting its his unknown father. We already know that his mother is from a fallen clan/sect, and I think its a stretch to connect her to the blood demon. But his unknown father could totally be related in some manner, whether he's a relative, descendent, or (I really doubt this) the former blood demon himself. We'll know easily if its his father or mother as long as he just hands over the sword to his sister for a moment.