Tokitou Jiroubou Seigen

One of the magi invited to Adra, the Castle of Separation.
The Shugendou he practices is originally something optimized for the Far East, but thanks to his ancestors’ admiration for the West, he also possesses a Magic Crest. Though he is unsuitably good natured for a magus, the fate he met in the Adra incident can be clearly seen in the story.
Though it was thought he would leave the stage at that point, he made a brilliant return in the Grand Roll incident. With the Mystic Eye beneath his eyepatch and his prosthetic arm made from a ghost root, he has an unnecessarily high amount of protagonist power. After inheriting the magecraft of the Castle of Separation and taking care of Rosalind, the younger sister of his departed friend Heine, this author couldn’t help but apologize constantly while writing. “You’re such a good guy. Sorry for putting you through all this.”
After the conclusion of Case Files, he appealed to a number of magic organizations in order to help save Rosalind, but that’s a story for another time.

Lord El-Melloi II Case Files material: Lord El-Melloi II Case Files Glossary