The Villainous Feudal Lord Reincarnates in the Ninja World

So, I'm a pitiful (not really) princess who was arrogant and decadent, lived for pleasure, and backed the wrong side despite having more power than ability. Then, after dying, I was reborn in what seems to be a folklore-inspired version of Japan, where I became a frail (actually) princess who was just as arrogant and decadent, lived for pleasure, and had status without ability, with no side to back at all?

This is a tough one...

Then let's not bother!

Flip the table!

I don't care about your noblemen's unspoken rules!

Even aliens will kneel and swear fealty to me!

Uchiha! Seize the throne for me! I'll make you officials! High-ranking officials!

Senju! Capture the Hyuga clan for me! I want to build an ice pond and orchard!

Hyuga! Put your Byakugan to good use and screen them carefully! I want the right to claim the first night of every man in the capital!

Anyway... I'm an utterly immoral tyrant, yet somehow I ended up unifying the continent.

Just as I was thinking that I could maybe (not maybe) brag about being the second Qin Shi Huang, the Otsutsuki showed up to plant a tree!

Invincible on earth?

Enemies from the heavens!

Damn it! I am the greatest emperor in history! (According to my subjects.)

Mine! It's all mine! This entire universe is mine!

Everyone in the universe will speak Chinese!

[Please note]

The main story is written in third person.

Before being reborn, the heroine was a princess in a feudal dynasty in a parallel world. That dynasty roughly corresponds to the period of the Wei and Jin dynasties, when the Five Barbarians ravaged China. (This only establishes that she comes from a chaotic era; it has no real significance.) But since this is a fictional setting, I'm making it up as I go! (I just want the Warring States ninja world to get a taste of genuine feudalism. Please, give me some feudalism!)

The heroine is a genuinely evil, ambitious person, but also a capable Chinese-style feudal ruler (still too progressive for the ninja world). She is not lawful good, so please keep that in mind.

(The heroine isn't insane enough to actually compare herself to the First Emperor. It's just a gimmick to show how arrogant she is. Please don't flame me, wahhh. If you do, I'll change it.)

A reverse harem story.

Power fantasy with no angst, not a farming novel.

Theme: As heaven moves with vigor, a gentleman should strive ceaselessly for self-improvement.