Sekido was a demon like tanjiro he had a bamboo muzzle like tanjiro the only difference was that he was a grumpy/angry demon he was a good demon like tanjiro though but when he conquered the sun after tanjiro he could finally be able to speak he was still grumpy and angry around his brothers Aizetsu, Urogi and karaku but when he was around you..he wasn't grumpy/angry much when he was around you he felt a connection around you (Read long Description for more information)