Watakushi no Koto ga Daikirai na Gitei ga Goei Kishi ni narimashita

Synopsis:

Willemina, the daughter of a duke, was harsh with Nigel, her foster brother, whom she unexpectedly had, believing him to be her father's "illegitimate son." Although she can not apologize for it for years, she eventually comes to accept her foster brother. Her foster brother becomes a knight-at-arms after a few years, but things are not as they appear. She is unable to apologize.