The Ninjutsu Scumbag's Counterattack

Hundreds of years ago, the world was in a harmonious farming society, but a group of alien beasts who didn't know where they came from attacked. All mankind fell into turmoil. Finally, when humans were attacked by alien beasts and only survived 30%, a savior came from nowhere and imparted powerful power to the people of this world, allowing these three people to defeat the alien beasts in one fell swoop. In order to commemorate that era and the god who imparted power, people have since called this use of power ninjutsu, and that god is called the god of ninjutsu. Now, our protagonist Qian Maple, before graduating from the ninjutsu school, he was the worst ninjutsu student in the school. So, why can he avenge his disgrace in the National Ninjutsu Competition despite being known as a bad guy and a waste? What kind of counterattack is he looking for? This novel and its characters are purely fictitious. Any similarity is purely coincidental and should not be imitated.