Ryuu Kusari no Ori -Kokoro no Uchi no “Kokoro”- - Chapter 5[LN] Volume 4: .4

Lyle Walt is a young noble boy and heir looking forward to the day he can inherit his family’s territory. Except around when he was 10 year old, his parents started neglecting him more and more in favour of his little sister, Celes.
On his fifteenth birthday, he is challenged to a duel by his sister to see who will inherit the household and horribly loses, being cast out of his family. Afterwards, he gets treated by the family groundskeepers and receives the family heirloom Gem from him that Lyle’s grandfather had entrusted to him. From there, he begins an aimless journey with his childhood friend and former fiancée, Novem, and the Gem-turned-Jewel that houses the memories, personalities, and Skills of seven of his ancestors.

Shaymon, the man who has achieved the apex of dark magic, is framed as being a Demon King and is killed.

On that day, the fog blocked everything.

On that day, he became the captain of a ghost ship.

On that day, he stepped through the thick fog and confronted a completely subverted and fragmented world—the old order had vanished, strange phenomonoms dominated the endless seas beyond civilized society, and isolated island city-states and fleets of ships challenged the sea that had become the last ember of lights for the civilized world. All of this while the shadows of the old days were still stirring in the deep sea, waiting to to devour this world that was about to die.

But for the new captain of the ghost ship Vanished, there was only one question he had to consider first— Who knows how to drive this ship?!

- Description from Novelupdates

For the wine to be drunk on her wedding night to actually have been a cup of poison and for the one to poison her to be her husband, who would believe it?