Based on the erotic doujin game by Circle ☆ Fairy Flower (サークル☆フェアリーフラワー). 
 
My name is Milia. I'm the princess of the kingdom, and I was given the title of hero from the heavens! Well, the title of hero was actually supposed to be given to the son of the king who took me in, but I got pissed off..., so I took it away from him☆ And by the way, I had him executed for being a loony☆ I'm going to die for being so useful to this cute little me, so I won't have any regrets, right?♪ I've grown up and become a great hero, but lately something's been strange. "Do you want to see my pants? That's how normal it is. Why don't you look at it as much as you like?" What is this!? What is this!? What's going on!? I am the most beautiful, strongest, invincible, and brave princess! I'm supposed to be..., What's going on? I'm getting naughty all over the place, aren't I? 
 
(Source: Getchu, translated)

Yuusha-hime Milia