Under the Oak Tree is a Manga/Manhwa/Manhua in english language, Drama series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.nl fastest updating comic site. The Summary is

The daughter of a duke, the stuttering Maximilian, married a knight of lowly status at her father’s coercion.
After their first night, her husband departed for an expedition without another word.

He comes back three years later, this time as a famous knight in the whole continent.

How would Maximilian face him on his return?

"The more I think of you, the more lonely and lonely I become. I don't know why I can't quit even though it's so painful."