Warning: Spoilers ahead.
This ep follows I'm Quitting Heroing - Episode 7
, and boy is it filler. Boring filler. There’s about 3 minutes worth of new useful information. Then the rest is filler disguised as a touching character development story.
It begins with Leo reading a book in his room. Shutina comes in saying Echidna is summoning him to the throne room for a promotion to leader. The generals and Leo plan to reveal to Echidna that he is the true identity behind Onyx. And Leo will also explain why he lied about his reason for joining the Demon Army.
Leo has a flashback to his memories of the old world triggered by the book. The book is about a demon from back then named Eibrad.
Back in Tokyo, in the old world, Leo was protecting humanity and killing demons as usual. Then he investigates a demon imp who is supposedly preaching coexistence with humans. The rumors turn out to be true. Eibrad is a wise, empathetic imp.
Instead of killing Eibrad, he decides to take Eibrad into custody. But they have to walk all over Tokyo to get to the extraction point.
It’s during this walk that Leo and Eibrad get to know each other. From Eibrad, we learn the demons didn’t mean to start a war with humans. Their king, Belial, was able to open a portal to the human world, which is an extremely rare and difficult thing to do. The lower demons like Eibrad were curious about the Human World, and also wanted a place with less conflict and war than the Demon World. But as soon as they arrived in Tokyo, some lower demons like ogres went with their instinct and started attacking humans. Which is how the war began.
Eibrad says they tried to go back through the portal to the Demon World, but it was closed from that side, probably from someone powerful jerk like Belial. He suspects spies came in the first wave through the portal just to report back to Belial that humans are weak and can easily be conquered.
From Leo’s side, he explains he was designed to protect humanity. He doesn’t have a gender and he’s not actually human. He will live on forever, his only purpose saving the world.
Eibrad feels this is a sad existence, but the robotic Leo doesn’t really understand feelings and stuff this early in his life. The ep spends forever having Eibrad explain why this is sad. How his reason for living will be taken away from him if the war ends, which is not fair. Leo tries to assure him that he’ll probably be killed off before he gets sad about his purpose in life.
As the extraction team takes Eibrad away, Eibrad has Leo promise that he lives his life the way he wants. And that he will look for another reason for living when humanity no longer needs him. Leo doesn’t really understand, but he agrees to do so.