Echidna

Echidna is the demon lord who is said to annihilate mankind. After being defeated by Leo Demonheart, she had to back off with her army.

She is the titular female protagonist of the Yuusha, Yamemasu series.

Appearance
Echidna is a woman of average height. She has horns and long, flowing pink hair reaching some way down past her shoulders. She has deep, golden-colored eyes. She wears one pair of red earrings, thigh-high boots, a red dress along with a black belt having a golden suspender.

Even though she has a young and beautiful woman's appearance, she is over a hundred years old.

Personality
It is said that she is an unruly and cruel person. Despite these rumors, Echidna is generally easy-going, cheerful, and relaxed. As long as she isn't directly provoked, she's perfectly fine with "live and let live," although she occasionally voices the desire to burn up people en masse when she gets impatient.

Echidna is really different from her ancestors which is shown when she gave the order to avoid any unnecessary bloodshed and told her subordinates to rule the occupied territories in peace.

She is at her core a very kind and noble woman. The reason she pursues the Philosopher Stone is because she wants to help the Demon World and give her fellow demons a peaceful place to live where they can live happy without fights and bloodshed.

Echidna deeply cares for her subordinates, like when she asked the Great Generals to help Steina because she thought was very stressed, she also an be very thankfull towards her subordinates for the work they do, she even organized a private dinner for Lord Onyx because wanted to personally meet and thank him for his work despite being a newbie in their army. Although she is prepared to destroy mankind in order to retrieve the Philosopher Stone she admites has nothing against them. She also does not hate or discriminate humans, and she'll welcome anyone who wishes to join her army. Echidna says she doesn't blame mankind for considering her and her army as the villains because they made an invasion of their territory. However, she deeply hates Leo Demonheart for stopping Echidna and destroying her army.

Though an imposing and intelligent woman, she has shown a bit of a childish and comedic side, specially when she's drinking alcohol.

Background
The "'Demon Lord" who tried to invade the human world in order to retrieve the Philosopher's Stone.

Leo Demonheart
She seems to him because he's the only obstacle between her and the philosopher's stone, the only item that could save the demon world. After he sneaks into her army thanks to help from her generals, he improves her army bit by bit while also trying to learn her motives for the stone. He deems her worthy and after he reveals himself to her, he guides her and the generals to the near mountaintop to kill him and claim his heart which is another philosopher's stone

Steina
Even though they're 300 apart in age, Steina is the closest person to Echidna.