MTL - I Just Wanted To Retire and I Was Forced To Become a General - ~ Side Story・The marriage under the sunset is my lost youth

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.

Known as the country’s top onmyoji, Yuuma Kisaragi, who lived to the age of 99, awoke to find himself in an unfamiliar forest. A voice echoed in his mind, revealing that he had been reincarnated into another world at the age of 20.“Good morning, Master. Skip the greetings and please defeat the goblin in front of you.”The voice belonged to a skill acquired during reincarnation called “AI,” designed to assist Yuuma in his new life. When the skill, AI, took over the form of a golden-haired fox yokai, the familiar shape of Yuuma’s shikigami, he decided to embark on a new life alongside AI-chan.The onmyoji and AI-chan’s second life began, tackling various challenges and formidable enemies with the strongest spells and shikigami.

One imperial edict and the family’s calculation, the sweet, adorable her met the cold him that was up high. She became his little princess consort. Everyone said that Prince Ying of Western Xuan Empire was shockingly ugly, cold-blooded and ruthless. They laughed at her that she had mistakenly entered the tiger’s den with her life in danger. But she just laughed that everyone in the world couldn’t see the wider picture, and were stupid and ignorant. The ugly appearance was actually beyond gorgeous, cold-blooded was actually gentle and sweet. She only wanted to hide him away and not allow other people to peep at him. “Big Ice Cube, take off your mask and let this princess have a look!” She propped up her chin with saliva flowing down.

“Want to look?” A certain person’s lips hooked into a devilishly charming smile, saying. “Then first, hand over some down payment…” This is the story of a sweet adorable female and a two-faced male’s journey to fight enemies and kill strange things, while pursuing a romantic relationship that was absolutely full of loving spoiling, hilarity and hot-blooded action.

- Description from Novelupdates

When he did not know her true identity, he treated her very badly, he disliked her too much, she was not elegant enough, she was in the way...Only later did he realize that the woman was his legal wife! He repented, tried to recover her feelings, but she was determined to divorce him.