My Yin-Yang Wheel-Turning Technique Has Me Falling Apart

[No System, not a goody-two-shoes, transmigration, another world, cultivation, fiercely protective, prince, little girl, myriad races, abyss, a touch of Lovecraftian horror. Probably a single heroine, since I usually don't write harems and don't really enjoy doing so.] Liu Tian, a young man from Blue Star, transmigrates to a cultivation world and becomes a crown prince. In the palace library, he finds a sealed cultivation manual. After practicing it, he splits off a white-haired, red-eyed younger sister. But why does she seem a little... off? Father Emperor: Xiaotian, you say you've split in two? Let's see if it's a heart demon. If it is, I'll cut it down in one stroke. Heh, this daughter of mine is such a delight. Empress Mother: Xiaoya, come here. Mother will dress you up as the prettiest little princess. Liu Tian: Xiaoya, good girl. Wait, why are you tying me up? Liu Ya: P-please don't abandon me. Big brother is so naughty, always flirting with other girls. We're one and the same, so you can only be mine, big brother. It's not incest if we're the same person, right? (ಡωಡ)hiahiahia There'll be illustrations later, hehe.