i kinda feel like the story was mostly to make time and make him lower his guard, those kind of mind techniques are not strong enough to be used if the other side resist most of the time, or he wants to be killed, like he told him "i am a blood demon that killed his own master with this art" and now he is giving the mc the technique, though if it was either one of those it was poorly conveyed so most likely blood demon just told the story just because and the mc will make the blood art his own, i just hope that if he does integrate the blood art it will at least take time and some drama, if its gonna be like that at least be entertaining