Manga with a lying reincarnated child main character

Question

I remember the gist of the story; it was about a reincarnated main character who lives in a child's body.

The main character then discovers an Elf girl who he lies to and makes her believe his chunibyo fantasy, but the truth was that these lies were true and he didn't know. He managed to save some other elves who also believed the "lies."

After that there's a kidnapping of his sibling who he saves, he fights with a bad guy and I don't remember much else... He was reincarnated into the body of a noble child from a fantasy setting, unfortunately I read this manga in 2018 and don't remember much of it. I only remember that the elf girls he rescued created a group that follows his orders. A more specific clue would be that he met with one of the elven girls who was smart, and she had recreated soap and had started to sell it causing her to be rich.

Answer 1

I believe you are looking for Kage no Jitsuryokusha ni Naritakute, also known as To Be a Power in the Shadows!

The manga starts out with the main character dying in our world and reincarnating in a world with magic. He pretends to be weak, while training to be the strongest. He attacks a bandit group to test his skills and equipment. Afterwards, he finds a cursed elf that he heals. He tells her that he is fighting the "Diablos Cult" from the shadows, and asks her to join him in fighting them from the shadows. She agrees, enamored with him for saving her life.

When his sister is kidnapped, we find out that he has convinced 7 people of his lie about the cult. One of them explains that they believe the kidnappers are one place, he randomly throws a knife that hits a spot on the map in the opposite direction and says the kidnappers are obviously at that spot instead. His group then attacks that spot. Then we find out that all the lies the main character has been saying are actually true. There is a Diablos Cult base there, and they did kidnap his sister. However all his actions and thoughts say that he doesn't actually believe any of it and thinks his group is just playing along with him when they find evidence to back up his claims.