So i remember one of his work, 1 series with 3 chapters.

The story was about a boy who was from somewhat onmyouji line and he have big sister that was far more better than him in combat.

But he still elected as the heiress by his grandpa because he have the ability to sense demon while her big sister didnt have it.

He also entrusted to protect a girl who now become a part of his family and actually a fox demon

His job was to protect peaceful demon that side with human from another vicous demon.

edit : it was from lying mii kun authour, found it