I Became the Best Forensic Doctor After My Betrayal - Chapter 57 - 57 Jealousy

Takahiro Nao, a 25-year-old burdened by crushing debt and driven solely by his love for his struggling family, meets a tragic end—until a mysterious Goddess of Benevolence offers him a second chance: reincarnated in another world, and his efforts there will provide for his family back on Earth. Awakening in the body of Naoki von Blackmore, a disgraced “Failed Hero,” Nao is thrust into a realm of sword and magic, monsters, and war, tasked with the impossible mission of defeating the Demon King. With newfound powers, a shadowy past, and the weight of two worlds on his shoulders, he must battle not only relentless enemies but fate itself. Blending emotional depth, thrilling action, moments of humor, and a spark of romance, this gripping isekai adventure asks: how far would you go—and what would you sacrifice—for the people you love?

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates

— Doing good deeds brings blessings.— If actions meet societal standards, user ‘Jeong Da-on’ will have their restrictions reduced.Blessings for doing good deeds? Even if I was the Demon Lord in my previous life?It’s been 19 years since I ended my tumultuous life as the Demon Lord and reincarnated on modern Earth.I was caught by the system and forcibly turned into a Hunter. And now I have to do good deeds to regain my original abilities?“Hmm… Beating bad guys to death counts as a good deed, right?”That doesn’t sound too bad.Modern society is the perfect place for a demon to thrive, after all.

Rein Aster was just a herbalist farmer from a border village.A nobody. A background NPC in a story filled with prophecy and divine warfare.But by chance—or fate—he saves one of the 7 Demon Lords during a catastrophic war event. Instead of killing him, she falls for him.Obsessively. Violently. Eternally.And then… so do the others.Each Demon Lord tries to trap Rein as her personal lover/pet/priest/husband/god, building dungeons, illusion palaces, soul prisons—but Rein keeps escaping. Quietly. Cleverly. Never fully rejecting them—but never submitting, either.Why?Because Rein realizes something:The gods are worse than demons.The heroes are tyrants in shining armor.The world is collapsing—and he’s the only one they all listen to.So he hatches a plan:Use the Demon Lords’ love to take over the world.Pit them against the heroes. Unleash them on the gods. Make them fight for him. Make them kill for him. Then tame them all.Not as a king.Not as a savior.But as the lover they would burn the world for.__________The yanderes here are darker than what you might be used to.You have been warnedThe entire novel has a dark feel. Atleast read the first two minor arcs