Akuyaku Reijou ni Nanka Narimasen. Watashi wa『Futsuu』no Koushaku Reijou desu! - Chapter 213.2: Saintess’ inheritance and weapon.

Ian Percus, the second son of a countryside Viscountcy.

One day, he received a love letter from the future.

‘If we don’t protect the future, the world will perish.’

With an ominous warning scribbled by someone

When the human princess, Lareina is sent as a bride for a peace treaty between the demons and humans, she ends up in a political marriage with the second prince of demons, Prince Azrael. Lareina falls for his gentleness that sets him apart from the rest of the demons in her eyes but on the night of their wedding, he is deployed to the war.Years after his abrupt departure, Azrael has finally emerged victorious and returned. However, much to Lareina's dismay, he has brought back a beautiful demoness with him. At the receiving end of his hatred, a heartbroken Lareina tries to save their marriage until all her hopes are shattered. Determined to carve a way for herself, she decides to end the marriage but she is met with a new challenge when her seemingly uncaring husband suddenly refuses to let her go.

Qiaosheng, you are the one who saves me, yet you are also the one who gives me hell. If we cannot grow old together, I’d rather we’ve never met before.

- Description from Novelupdates

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.