poor demon lord, who have his name forgotten by his descendant.
edit : i rate this 7/10, because i see the plot is kind of stupid. the MC have told anyone that he is the demon lord and give a proof by telling that magic that using his source of power won't hurt him, but the other did not even believe him. he have such overwhelming power but the academy label him as unqualified. he can do magic when he just born and the parents see him as genius. he can do long lost magic, but the other just see it as amazing and did not questioning him about how can he do that or how he can know that magic. and more, it seems that the character here is lacking of intellegent.
p.s. but i can still enjoy it, just by closing my common sense, that's it.