After this episode, there is no longer a way back to the Modern Era. All paths known to everyone have been Destroyed or deactivated permanently.
Towa uses the Grim Comet's own energy to upgrade her attack to Shooting Star Azure Dragon Wave.
Rion extracts the power of a Kyokon from the mountain by using the apple seed Riku kept.
The Grim Comet is actually a cocoon holding a powerful entity.
Black Hiraikotsu is an upgraded model that dispels evil energy. Making it stronger than the original.