He is bound by his original programming to protect humans, even if they hate him.

Leo was one of twelve "Demonheart" units created by humanity to fight off an invasion of "Demons" (which were actually extra-dimensional monsters). While the other units were eventually destroyed or deactivated, Leo's unique ability to "auto-evolve" and his immortality allowed him to survive indefinitely.

The episode primarily consists of a long conversation between and the Demon Queen Echidna . As they share a drink, Leo finally reveals the truth about his past and his true nature.

This episode provides a massive "lore dump" that recontextualizes every previous event in the series.

Yuusha, Yamemasu (I’m Quitting Heroing) Episode 6, titled serves as the series' most significant turning point. It shifts the show from a lighthearted workplace comedy about rebuilding a demon army into a somber post-apocalyptic science fiction drama. 🔑 Key Plot Summary

Episode 6 transforms Leo from a goofy, overpowered protagonist into a tragic, weary figure. Description

Leo reveals that his primary directive is "Save Humanity." However, because he is immortal and infinitely adaptable, he has become so powerful that humanity now views him as the greatest threat to their existence. 🌍 World Building & Lore

For three millennia, Leo has watched civilizations rise and fall. He has served countless kings and saved humanity hundreds of times, only to be feared and eventually exiled every single time once the threat was gone.