Global Reincarnation: Only I Know the Plot - Chapter 25:

In the kingdom of Veridian, Prince Lucien Damon is known for his charm and charisma. But his kingdom is facing economic ruin, and his father, the king, in an effort to alleviate the economic strain on his kingdom has arranged a marriage between Lucian and Prince Alexander Silver of the neighboring kingdom of Avaloria.In the kingdom of Veridian, Prince Lucien Damon is known for his charm and charisma. But his kingdom is facing economic ruin, and his father, the king, in an effort to alleviate the economic strain on his kingdom has arranged a marriage between Lucian and Prince Alexander Silver of the neighboring kingdom of Avaloria.

Gawain is dead and was transmigrated, but there was a slight problem during the process.
After floating for more than a hundred thousand years on a different continent, he felt that he might need a body to become a complete transmigrator, but he did not expect that…

- Description from Novelupdates

The world is terrorized by the powerful Black Witch who has been sealed in the moon. Every ten years, the night of Hexennacht arrives and a chosen witch must battle the Black Witch in hopes of finally defeating her.

As the current decade’s Hexennacht approaches, a mysterious girl named Kagami Kagami arrives and meets Horinouchi Mitsuru, the daughter of the previous Hexennacht representative.

It takes place between Kyoukai Senjou no Horizon and the City Series, two other series by the author.

In Japan of 1992, just after the economic bubble burst, society's public safety began to deteriorate. Xu Tianze finds himself transmigrated into the body of a detective named Aoyama Hidenobu, and the moment he opens his eyes, he discovers himself bound up tightly...Entering the new century, a prestigious magazine proclaimed that although Japan has lost a decade since the 90s, they gained a legendary figure like Aoyama Hidenobu.Regarding this, some Japanese nationals expressed: 'Damn it! We'd rather lose another 100 years than have this traitor to our country!'This book is also known as 'This Tokyo is Somewhat Hot.'PS: The protagonist is a rascal, acting with contempt, decisive in killing and fighting, purely for the thrill, not for the faint-hearted.