The Eminence in Shadow: Shadow Side Story summary:
Cid is a boy who reincarnated in another world, and decided to enjoy a scenario of being "the eminence in shadow, someone who meddles with the story from the shadows, and exhibits his true power in secrecy." Thus unfolds the story of him and the secret organization he leads—Shadow Garden—as well their their pleasant friends! An easy-going 4-koma manga starts right here and now! (Source: Kadokawa, translated)