I think it should start with Mundus giving out his plans as to taking over the human world, after he overthrows the old master. Then Sparda is sent to the surface in order to study humans, and whilst there he travels around in a disguise so that he is not found out. Covering his face, and he is studying Mallet Castle, as to which he finds a priestess residing on Mallet Island, called Eva. He falls in love with her beauty, yet fears that if he goes with her he will be killed. In an attempt to win her over, he gathers an army to fight against Mundus, to gain her love. She instantly feels for his heroic side, seeing him as a demon with an honest heart, and Sparda rallies a group of knights, and a group of demon warriors that were his friends and he goes into the Underworld whilst the war is being waged outside. Seals Mundus, and then rised Temen-Ni-Gru, and fihts to the top where he seals the realms from each other, and leaves his power there. And returns to Eva, and has Dante and Vergil, and then it could end with him disappearing.