The Ruined Ending made by a Baby

I was reincarnated as a character in a game who must die for the hero to awaken.
 
Other people only reincarnate once and live comfortably,
 
but I died five times for the hero’s awakening.
 
So, on the sixth time, I just killed the hero.
 
But then…
 
[SYSTEM]  
Detection of malicious force harming the hero! Warning! Warning! Emergency! Emergency! Hidden character detected approaching the malicious force!
 
Suddenly, I reincarnated as a hidden character.
 
“Eubyaaa?! (What the heck?!)”
 
And not just any character, but the youngest daughter of the demon king, the game’s final boss.
 
[SYSTEM]  
A new mission has been triggered. Do you accept? Y/Y
 
I, who always died as the hero’s lover, am now the demon king’s youngest daughter in this life?
 
I actually prefer this!
 
*
 
…or so I thought.
 
“We’re all going to die anyway, so stop resisting.”
 
“I don’t mind dying if it’s for the demon king!”
 
But I don’t want to die!
 
“Boss, there’s a dungeon over here.”
 
“This dungeon has dancing flowers.”
 
So, I worked hard to help the demon king grow.
 
#Let’s see the destruction ending
 
But then…
 
[Am I the true master?! Unveiling the world’s secret!]  
What the heck is this?