The War Between Sentinels And Demons

For the last millennia, sentinels and demons have been fighting a war against each other. Millions have died since then. Gil, a young sentinel, and Maria, a pure-blooded vampire, lose their parents to winged sky dragons. Tempestas, a demon with the appearance of a middle-aged man, decides to take them in. Tempestas lets the two live in his home(the demon realm). He trains Gil and Maria after seeing the potential they have. Before he dies, he tells Gil and Maria of his dream, and the two swear they'll make it happen. Gil and Maria then set out to make a world where demons and sentinels can live in peace.