Flea to Fearsome

Ethan is reborn as a flea. A system binds to him that raises his body a stage at a time whenever he takes in essence blood. Fiona, the best-known student at Dawnrealm Academy, signs a contract with him, which makes a flea her contracted beast, and the other students laugh at her over it. He feeds and works up through the stages, from the flea he started as to a beast that swallows stars. He goes with Fiona into the trial realm and they get through it. In the champion's realm they fight the strongest opponents there. He fights again in front of Dawnrealm Academy at full strength. He then brings the Crimson Phoenix under his control, and after that the two of them go against Crown Academy together.