Even with the little time they've spent together, Malachi still hadn't been able to find answers regarding the mystery surrounding Leo.
From what he could see whenever he looked at Leo with his ability, it was obvious Leo was different from him, his son, and also his own daughter, Yuki. Yet, Malachi wondered how it was possible that a man who had no crystal heart in him was able to become supernatural just like him and David.
Malachi knew there was a lot in the new world he could not understand yet and might never understand, but he felt the Leo case might even be a special one.
Aside from this, there was also his sword that ironically had a crystal heart that Leo didn't.
Moreover, there was the mystery of how Leo got stronger since he had no crystal heart in him to use the crystal hearts from the monsters they killed.