What Does It Mean That I Am the Savior of the Previous Term?

When I woke up, it started to rain heavily, and the country issued a notice that great changes had taken place in the world and the passage to other worlds had been opened, bringing destruction as well as opportunities. In a new catastrophe, countless heroes emerged, and endless disasters followed. The Beast Tribe, the Feather Tribe, the Shura Tribe... When all the alien races were attacking the gate where the two worlds intersect, a figure holding a thunderbolt in hand stopped in front of the door. "I will stop you for the sake of the world behind me!"