Ryuu Kusari no Ori -Kokoro no Uchi no “Kokoro”- - Chapter 1.6

Qin Chen was transmigrated to the Taiyi Holy Land where he became a servant in charge of sweeping the floor. However, on his 16th birthday, he was rewarded with a system where he was rewarded whenever he signed in at a new place.

When he signed in at the Empire Ruin, he was rewarded with the strongest Chaotic Holy Body and the Chaos Emperor Scripture.

When he signed in at the Demon Sealing Land, he was rewarded with the Probationary Royal Armies.

When he signed in at the Alchemy Palace, he was rewarded with the Divine-grade Alchemy.

When he signed in at the Herb Garden, he was rewarded with an Immortality Elixir.

When he signed in at the Empire Palace, he was rewarded with the Emperor-grade Divine Art, Revival.

…

Qin Chen thought he could just spend the rest of his life signing in at different places until he became invincible.

However, when the ruin of the Great Kingdom appeared inside the holy land, people from other holy lands, prestigious families, and even ancient empires gathered to defeat the All-Powerful Demon King who appeared with the ruin. The Demon King had killed countless people and had planned to destroy the Taiyi Holy Land.

Qin Chen was left with no choice but to step up. When he killed the Demon King with a single slap, he sighed, “Why do you guys have to force a mere servant to act?”

Thanks to the Goddess, he was reincarnated into nobility!　That should have been great―― but the skill he got, 【Toxin Decomposition EX】 was simply too plain, and he was made fun of everyday at home……

His Royal Highness the King of Han, who was afraid of the dark and ghosts and loved to cry, has always been the good baby of the princess.
Until one day, His Royal Highness the King of Han found a book in the bookstore…
Picture book?
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Search keyword: Protagonist: King of Han, Princess of Han

- Description from novelbuddy

She is an expert in medicine, the only daughter of Yun Tian, Yun Valley’s master.

Her parents died, leaving her alone in this world. She fell from heaven to hell. She had a marriage prospect but her future husband broke it off. The entire world view her as a joke.

She blossoms in Feng Yun Hall, with unparalleled wisdom and startling beauty.

Against all the people eager to make a move, she lifts her hand first. Kill the chicken to warn the monkey.

But nobody knows that the soul within her has long been replaced by someone from another world.

She has no regret in the past life and originally plans to live an idyllic life, but because of the same question from the past life, she gives up the peaceful life and steps into the power struggle for imperial power.

- Description from Novelupdates