Final Demon King

Sudden memory unblock, suddenly gain strength! A high school student suddenly learned that he was a white mouse in the laboratory, his family was fake, and his sister was forced to serve that organization in order to protect himself! What should I do if I suddenly gain strength? Until, a girl with the title of witch said to the high school student, "Would you like to sign a contract? As long as you sell me for the rest of your life, I will help you get rid of all this!" At that time, the high school student agreed without hesitation! Give your soul to the witch of hell... (