Seiken Gakuin no Maken Tsukai

In the fantasy story the demon king Leonis sealed himself away for 1000 years in order to prepare for the final battle but when he woke up he found himself in the body of a 10yearold boy A beautiful young woman named Lisellia from the Holy Sword Academy then says to him Why were you locked up in such a place Its OK now this big sister will take care of you Under Lisellias care Leonis is shocked to see that the world has completely changed Bewildered and confused Leonis finds himself enrolling at the Holy Sword Academy ANN