Summary Blood System from Kainu Manga
Blood System summary: In a dangerous world teeming with monsters at every turn, the kingdoms placed their hopes in the System Users, powerful adventurers who grew stronger faster than anyone else. Among them was Novis, one of the most righteous of all. But when a quest goes horribly wrong, Novis’s system becomes infected... and his first new quest is a thirst for blood. The world isn't as simple as Novis once believed. The line between monsters and humans begins to blur, because Novis is no longer just a man. He’s a vampire... a vampire wielding the kingdom’s most powerful system.
