MTL - Rebirth of the Film Emperor’s Beloved Wife - ~ 10 Guess it yourself.

Ethan accidentally rode the wrong train and ended up in Brynhildr Magical Academy where Wizards and Witches are taught on how to use Magic.As someone who didn't have any magic powers, he thought that he would be punished for being in a place where he wasn't supposed to be. Fortunately, due to a stroke of luck, the teenage boy managed to avoid the worst case scenario, and ended up staying in the Magic Academy to learn magic.Ridiculed by many for being magically crippled, Ethan strived to adapt to his new school life with the help of his new friends, who made him realize what True Magic was all about.

The age of darkness has arrived.

In a world fractured by conflict and haunted by shadows of the past, Kokushibo—the first Upper Moon demon—meets his end, only to awaken in a new life. Reincarnated as Crimson, a child born into a different family, he carries the memories of a past he cannot escape. Burdened by centuries of guilt yet indifferent to the present, he resigns himself to duty—until an unexpected bond with his newfound family begins to thaw his hardened heart. As he struggles between the weight of his past and the weight of the new life, Crimson must decide whether he will remain shackled to his former sins or embrace the possibility of peace.

The boy who Sneaks in My Bedroom Window