The Heroine’s Sister-in-Law in a Childcare Story

I was reincarnated as a villainous supporting character in a childcare story. A worthless imperial princess who obsessed over and clung to the adorable heroine’s eldest brother, only to end up poisoning the heroine and meeting her ruin. “I’m done with all of you from now on!” With that resolve, I prepared to run away. But after saving the heroine, everything went completely wrong. —Anyone who dares to touch my unnie, I’ll chase them to the ends of the earth and tear them apart. —The imperial family? An incompetent imperial family that only makes Titania miserable. What does it matter what happens to them? —Hahahaha, those fools call me a mad dog, so why are their heads so empty? If a mad dog chooses who to bite, is it still a mad dog? C-Calm down, everyone. I was planning to leave and enjoy dreams, hope, and money at a seaside villa with beautiful waves! You should all be happy too! …Or so I thought. —…I thought you had truly died, and I… His golden eyes, with my reflection held within them, overflowed with emotions I could not read. I felt as though I might drown just by looking at them. —…It felt like being trapped in an endless nightmare, Tia. Even as he desperately whispered for me to never disappear like that in front of him again, he gripped my hand as if binding me in place so I could not go anywhere. I was left speechless. And on top of that… —It’s okay if you hate my brother! It’s okay if you find my dad annoying! But please, don’t hate our ducal family’s money! …The adorable heroine suddenly handed me the key to the underground vault where all the treasures of the ducal family were kept. —Is everything too annoying? Then choose me instead of my brother. Don’t bother becoming something as troublesome as a duchess. I’ll stay by your side anytime, anywhere. What? Stop barking nonsense? Woof, woof, grrr, woof, woof! Even the heroine’s second brother, who had always looked at me like I was a thorn in his side, started acting strange. What is wrong with all of you?