Claudine...!

(from ebookjapan):

Claudine, the daughter of a wealthy French family, grows up to be a clever, beautiful, and charming person who is adored by all...

Claudine was born with a male heart. Although deeply hurt by betrayal from her beloved, she remains beautiful, noble, and deeply in love...

Riyoko Ikeda's work depicts a sad and beautiful single-minded love.