Reborn in Another World, I'm Doted on Exclusively by My Vampire Sister

The three forbidden domains: yandere, girlfriend, and little sister...

Don't ask! It just means I ended up in another world.

I thought reincarnating in another world would mean a peaceful, ordinary life, but this world is far more complicated than I imagined...

Who is she?

And who am I?

We don't know either...

I keep getting dragged into one inexplicable war after another, but along the way, I've made lots of friends.

I also keep growing stronger through these wars, eventually becoming the ruler of the demon race: the Demon King.

It's just... everyone looks at me a little strangely, and I have no idea why...