Glass no Shiro

In England, two sisters from a poor family, Malissa and Isadora, become involved in a noble family's search for their missing daughter. Isadora falsely claims to be the lost heir in order to claim the family's wealth and estate. She later intends to marry a foreign crown prince. However, some members of the noble family question Isadora's true identity. Meanwhile, Malissa discovers that she is actually the legitimate daughter of the noble family. The manga received the 1970 Shogakukan Manga Award.