Miki Kouda is one of two infants switched at birth by nurse Michiko Nohara due to a personal grudge. Biologically born to the impoverished Mine family, she was raised in the wealthy Kouda household, growing up with aristocratic privilege. This environment fostered a sense of entitlement and superiority in her, contrasting starkly with the biological Kouda heir who was raised in the slums. As a teenager, Miki aspires to become a successful singer, mirroring the ambitions of the other switched child, Nozomi Mine. She engages in a persistent rivalry with Nozomi, mistreating her based on perceived social hierarchy differences. Miki utilizes her family's resources and influence to propel her singing career, frequently attempting to overshadow Nozomi's efforts. Their lives intertwine through shared dreams and conflicts, yet their relationship remains adversarial. No official media beyond the core narrative expands on her evolution or resolves her storyline, leaving Miki defined by the initial switch, her privileged antagonistic role, and unresolved competition with Nozomi. The name "Mathilda O'Hara" does not correspond to any character details; she is exclusively identified as Miki Kouda.