When Felix had first handed Blake his sword, he had been wary of it, expecting it to harm him considering he was a sort of champion of hell but no such thing had happened, the system had instead even given him a disguise technique called the sun cloak.
Having never trained in the use of any weapon and arriving in this world with a set of sword skills in his arsenal, Blake had decided to stick with what was already working well for him and it was that decision that led to his current situation, his hand being burnt with an intense heat by the sword but having no wound.
With a few thoughts, Blake easily connected the dots, figuring out the reason why this holy sword was acting up now when it had been silent all this while.
"An unholy mind doesn't make you an unholy being but an unholy body definitely does the job"
That was the summary of Blake's current situation with his sword and at the moment there was nothing he could do about it.