Ragna Crimson 13 (manga)

Armed with knowledge of the future, Ragna joins the Solarian Church in a bid to prevent its imminent collapse. But his behavior soon incurs the wrath of his new comrades, including a young girl destined to become his mentor and a rambunctious saint who’s hungry for a fight. Meanwhile, on a faraway island, three of the most fearsome dragons alive gather to discuss their next move!