TV-Series
Description
Miki Koishikawa is the central protagonist of Marmalade Boy. She is a lively high school student who attends Toryo High School and is a member of its tennis team. Her background is defined by an extraordinary family upheaval: her parents, upon returning from a trip to Hawaii, announce they are divorcing and swapping spouses with another couple they met, the Matsuuras. This leads to the two families moving into a large house together, and Miki suddenly gains a stepbrother in Yuu Matsuura, a boy her own age. Earlier in her life, in junior high, she confessed her feelings to her male friend Ginta Suou, but the confession went poorly and left her heartbroken, though she eventually managed to rebuild their friendship.

Personality-wise, Miki is cheerful, friendly, supportive, outspoken, and good-hearted, with a tendency to be a girly girl. She can also be tomboyish in her energy. However, she has a less confident side: she is often insecure, whiny, clingy, and emotionally dependent on others. She is prone to jealousy and can be short-tempered, gullible, and stubborn. Her emotions are very visible, a trait that Yuu later admires. She is naive and emotional, often reacting strongly to the situations around her.

Her primary motivation is navigating the complicated new family dynamic and understanding her growing feelings for Yuu. She is drawn to him despite his teasing and cool demeanor, and she struggles with self-doubt when she sees other beautiful girls around him. She wants to be loved and accepted, and she seeks to maintain her relationships with her friends and family while figuring out her own identity.

Miki's role in the story is that of the main viewpoint character; the series follows her emotional and romantic journey as she deals with the blended family, her unresolved feelings for Ginta, Yuu's ex-girlfriend Arimi Suzuki, and the many misunderstandings that arise. Her relationships are central to the plot. She has a very close friendship with Meiko Akizuki, her best friend who supports her through her troubles. Her relationship with Ginta evolves from a childhood crush into a solid friendship, though it is briefly complicated when Ginta and Arimi try to drive a wedge between Miki and Yuu. With Yuu, the relationship starts with friction due to his teasing, then deepens into love. They confess their feelings for each other and begin dating, but distance (Yuu studying in New York), insecurity, and a false belief that they are half-siblings cause them to break up temporarily. Eventually, they reunite, discover they are not related, receive their parents' blessing, and marry by the end of the series.

Throughout the story, Miki develops from an uncertain and emotionally dependent girl into someone more confident in her own feelings and choices, though she remains emotionally expressive and caring. Notable abilities include her athleticism as a tennis player, and she works a series of part-time jobs, first at an ice cream parlor called Bobson's and later at a small decoration shop. Her ability to show her emotions clearly is highlighted as a strength that contrasts with Yuu's more reserved nature and helps them connect.