I Came From The Mortal World - Chapter 6 - Sacrifice

A mecha otaku is reincarnated into another world as Ernesti Echevalier (Eru). In this world there exist huge humanoid weapons known as Silhouette Knight. Dreaming of piloting those robots, Eru, with childhood friends, Archid Walter and Adeltrud Walter: together they will aim to become a Knight Runner, pilot of Silhoutte Knight.

Gilderoy Lockhart has just become Minister for Magic of the United Kingdom, and there are several uninvited guests in the office.

Dumbledore: “Minister, I have to tell you with great sadness that Moriarty Slytherin is the most hidden person in the European wizarding world!”

Lovegood, editor-in-chief of The Quibbler: “Look Minister, the Hogwarts Riots, the Himalayan Avalanche, the Gringotts Heist, the World Cup Opening, the Nurmengard Bombing, the Azkaban Defection , the Durmstrang riot, these mysteries all point to one person, Moriarty Slytherin!”

Platinum noble Lucius: “On behalf of the pure blood family, I strongly request the minister to launch a wanted request for Moriarty Slytherin! Oh, my minister, don’t look at me with greedy eyes, all pure blood money is taken by Mori Artie’s gone.”

Gilderoy Lockhart showed his signature smile: “Please allow me to introduce to you my young master, the greatest wizard of all time, the master of dawn and darkness, the master of ice and thunder, the legendary god of magic, Moriarty Slytherin!”

This is the story of a little wizard who only has magic in his heart and becomes the big boss behind the scenes in the Harry Potter world.

- Description from novelbuddy

This is probably the story of a modern man who became the Seventh son of Kangxi in the Qing Dynasty. This is probably the story of how the Seventh brother Yinyou worked hard and fell in love by the way. So there is no doubt that this article is ambiguous, and it is easy to guess who the couple is.

- Description from Novelupdates

Office worker Leon is reincarnated into a particularly punishing dating sim video game, where women reign supreme and only beautiful men have a seat at the table. But Leon has a secret weapon: he remembers everything from his past life, which includes a complete playthrough of the very game in which he is now trapped. Watch Leon spark a revolution to change this new world in order to fulfill his ultimate desire…of living a quiet, easy life in the countryside!