The return of the genius Sword Saint ~ I'm a failure with zero mana but actually the strongest~

The return of the genius Sword Saint ~ I'm a failure with zero mana but actually the strongest~

In a world where humanity has gained magic to fight against the Six Dragons that threaten to destroy the world, Yakatani Agito, despite the lack of mana in his body, has mastered swordsmanship and became known as the Sword Saint. In exchange for his death, he saves his own world from the threat of the Six Dragons, but their goal was to awaken an even more terrifying dragon 100 years after. The world would be destroyed if things continue this way. Agito, who was supposed to be dead, wakes up 100 years in the future due to reincarnation. This time, in order to save the world, he takes his sword and rises up once again.