Suterare Danshaku Reijou wa Kuro Kishi-sama no Okiniiri

Sophia Lenish, the Baron's daughter, was eventually kicked out of her home after the Countess abandoned her engagement. When she woke up in the forest where she, tired of walking, had fallen asleep crying, she had nowhere to go... Why did she have a sword at her throat?!

"You should live by my side."

"But I... will just be a burden."

This is the magic knight, Marquis Gilbert Forster, called "Black Knight" and Sophia was picked up by him.