If You Could Hear My Heart - Chapter 29 - 0: Spend the Night with Me

In a world where villains are crafted, not born, Vyan's life takes a detour from dull to downright dramatic faster than he can say “abracadabra.”Meet Vyan, the most ordinary knight in the realm, with all the magical prowess of a damp sock. Loyalty? He's got it in spades. Betrayal? Well, that's the surprise twist in his not-so-fairy-tale life.Framed and forsaken, Vyan is left with nothing but a grudge and some pretty gnarly scars, courtesy of his once-master, Iyana. Oh, did he mention she is the daughter of a marquess and the object of his unrequited affection? Talk about adding insult to injury.Just when he is ready to unleash his inner berserker, a butler comes along with news that makes his hair stand on end: Vyan is the last heir of the Grand Duke's mage dynasty!With power crackling at his fingertips and more mana than he can shake a wand at, Vyan is ready to show the world what happens when you underestimate the underdog. Will Vyan rise from the ashes like a phoenix, or will he crash and burn like a fire-breathing chicken? There's only one way to find out.

Haruto Hayase was a normal high school boy in his third year, living a quiet life until his younger sister, Haruka Hayase, joined the same school. Haruka’s beauty and charm made her the center of attention, quickly becoming the school’s prima donna. But when a notorious gang leader set his sights on her, he did everything in his power to protect her—only to fail tragically. Haruka was brutally assaulted and tortured, and Haruto himself suffered an agonizing death. However, in a twist of fate, Haruto is given a second chance, waking up a year before the events that shattered his life. Armed with the mysterious ‘Debauchery System Slave’, he vows to exact revenge on those responsible. This time, he will use his newfound powers of the system and charm to seduce the loved ones of his enemies. From their mothers, sisters, and lovers to their closest friends, Haruto will make them his. His enemies will suffer as he steals what they hold dearest, ensuring their downfall in the most devastating way possible.

The world that nurtured the civilization which reached the pinnacle of magic was on the verge of destruction.
The last survivor transmigrated to the past, when the magic civilization started growing, as countless mages were still fumbling their ways through the thorny paths of magic knowledge.
He, who came from the end of the magic era, aim to reach the pinnacle of magic.

- Description from Novelupdates

Crossing to One Piece world, he became Roger’s younger brother.