(from ebookjapan):

When opera diva Rei Mizumo falls in adulterous love with Richard, an English duke of the Conwall family, and is pregnant with his child, his childless wife Elisabeth tells Rei to hand over the child as the heir to the duke's family in exchange for forgiveness for their transgressions.

However, the child she gives birth to turns out to be twin sisters. Richard and Elisabeth decided in secret that the child named Michiru would be given to the duke and the child named Chiruchiru would be raised by Rei. Rei went to Japan first for work, and the jet carrying Chiruchiru was lost in the skies over Congo, Africa...!

Amidst the love-hate relationship between the twin sisters and their mother, who were separated by a strange fate, will Michiru and Chiruchiru ever meet again?