Mew Lettuce, also known as Retasu Midorikawa, is the third member of the Tokyo Mew Mew team. She is a thirteen-year-old second-year junior high school student who was infused with the DNA of a finless porpoise during the Mew Project. Before joining the team, Lettuce was a shy and timid girl who suffered from bullying by a trio of classmates often referred to as the Three Beckies. Her parents, Yomogi and Eizaburou, and her younger brother Uri provided a supportive home environment, and her family always encouraged her to be herself and believe that she would make true friends one day. Lettuce initially struggled with low self-confidence and was afraid to use her powers, causing them to become uncontrollable at times. However, with encouragement from Ichigo Momomiya and Mint Aizawa, she gradually gained the courage to embrace her abilities and became a reliable member of the team.

In her civilian life, Lettuce works as a waitress at Café Mew Mew alongside the other girls. She is known for being polite and speaking formally even to her close friends and family. Despite her timid nature, she possesses a quiet inner strength and will step into battle when her friends are in danger. Her transformed state, Mew Lettuce, has lighter green hair and removes her glasses, and her outfit is a green bodysuit with white antennae and garters. She wields the Lettuce Castanets, and her primary attack is a water-based technique called Ribbon Lettuce Rush, which can unleash high-pressure water blades. When in contact with Mew Aqua, Lettuce can transform her legs into a porpoise tail, greatly enhancing her swimming ability and allowing her to navigate underwater as a mermaid-like form. Over the course of the series, she develops a romantic crush on Ryou Shirogane, the leader of the Mew Project, and her growing confidence allows her to fully contribute to the team’s missions while maintaining her gentle and caring personality.