Basically after sending the dragons off to the war, Ruri felt uneasy
So she went with Joshua and the spy group to capture the king and the high priest.
Kotarou is here by now in his new body, and during the search (Joshua tell Ruri to sit back since if anything happen to her he's totally dead) Kotarou mention there's a part of the castle where his power have a hard time reaching.
As they get closer to where this weird power (and likely the high priest) is, Kotarou finally identifies it as the spirit-killing magic.
Basically, magic normally use the magic of the user + the spirit's power to cause the effect.
However humans don't have much magic, and they came up with the spirit-killing magic to forcefully extract the missing amount from the world.
If there's any lesser spirits nearby, they'd have their power drained away and basically die.
So the lesser spirits are told to stay back, Kotarou say higher spirits like him aren't affected so he tag along.
They eventually find the priests in hiding, fighting happen but even without being able to use magic the dragons are still physically stronger than the priests so it's an easy win.
Ruri then spotted the high priest and proceed to claw the shit out of his face.
At which point he grabbed one of THAT and threw it at Ruri.
Explosion.
Ruri is fine because Kotarou already made a wind barrier to protect her, just the impact sent her (being cat size atm) flying back.
After quickly subduing the high priest, they found a bunch of THAT and realize how dangerous it is if these are used in the war.
Joshua quickly try to inform the groups at the front.
In the mean time, while Ruri and Joshua are wondering how to deal with these boxes of THAT, Kotarou just tell them to shove it in Rydia's space, since THAT won't activate in there.
So they did.
Then Ruri did her revenge on the king and high priest (sadly it's not a lethal one)
Mean while back at the frontline.
Finn, the dragon who tried to at least maybe convince Asahi (nope) realized he's still alive despite the explosion from Asahi throwing THAT happening close to him.
Opening his eyes he found layer of water barrier protecting him.
Rin then made her entrance.
Basically earlier Ruri also heard that the king/high priest plan to let Asahi and the prince die in this war (i.e. suicide bombing with THAT), so Ruri sent Rin over to keep an eye on things.
Rin then basically deal with the issue by isolating anyone with THAT in a water bubble, then it's back to easy victories.
tl;dr You think there's going to be serious dramas? AHAHAHAHAHAHAHA.