how an insane demon half human became the 7th demon lord of insanity

Hello my name is Kira and I'm currently in an interesting situation "what the hell have you done child!?" said the head of the orphanage you see my situation is that I killed and drank the blood of a very abusive caretaker that adopted so I can do his chores. At first, I hoped that this guy was just drunk but no it was intentional I only lasted a week with him before I grabbed a knife and stabbed him 10 times in all his limbs I happened to be thirsty at the time so I treated myself and surprisingly his blood didn't taste bad which meant he started drinking after he adopted me hm so annoying. But to make this worse the head of the orphanage came to visit today so I couldn't create an accident. 'But wait Kira what did he do well he made me take his crap bucket out to the inferno whole Wich was created to dump the crap and incinerate it even though he could've done it himself and he would whoop me if I disagreed with anything he said and to make it worse it was a spiked whip I'm glad I wasn't completely human or I would've been crippled' so yeah he deserved death. oh yeah, I forgot to say his name that doesn't matter people like you don't need to know their names. I should probably explain to her "I'm talking to you girl!" she yelled "oh I'm sorry but he was a bad caretaker so I did that because he was scum I mean to read my mind if you don't believe me" I said bowing with a smirk as she did she understood"you still could have let him live" she said is the case you're wondering why she's acting like that you'll have to wait.