Dragon of World War

Xia Chengtian was born in an ordinary world, until one day the world changed drastically. He actually traveled to a world with dragons, his brother disappeared, and everyone forgot about him, except... A beautiful girl who stayed with him all the time. Xia Chengtian, who is in his third year of junior high school in this world, was admitted to a dragon-slaying high school. They are divided into "different dragons" and "dragon mutants". The method of slaying dragons mainly relies on "sword spirits". When entering school, the school will activate the "Sword Spirit" for new students, but after Xia Chengtian activated it, it was... Level "0"? This is something that no one has heard of in the world of dragon slaying. Normally, it is divided into "S" level, "A" level, "B" level, "C" level, and "D" level. There has never been "0" level. This makes his life in school not easy. What will Xia Chengtian face next?