Yuu Matsuura is the “Marmalade Boy” of Marmalade Boy. He is introduced in the first issue. His parents, Youji and Chiyako Matsuura get divorced and swap spouses with Miki’s parents, Jin and Rumi Koishikawa. Yuu and Miki become step-siblings.
Miki is immediately infatuated with Yuu’s good looks, but is put off by his rude personality. She proclaims that he is sweet on the outside and bitter on the inside, like marmalade. While Miki is totally against their parents’ arrangement, Yuu is fine with it.
Yuu doesn’t reveal much about himself to anyone. He just smiles and makes smart jokes, and derails the conversation whenever it starts to get serious. This prevents him from having a close friend or a serious relationship.
Miki soon meets Yuu’s ex-girlfriend Arimi, who only dated Yuu for three months, during which she tried to convince him that they would be a perfect couple. But Yuu just didn’t feel anything. It takes a long time for Arimi to truly get over him.
Yuu develops a strange relationship with class president Satoshi Miwa. Some people suspect that they are in love, but Miki and her best friend Meiko discover that it’s not that at all– it’s because Yuu has suspected since junior high that his dad is not his biological father, and that Yuu and Satoshi might have the same father, Yoshimitzu Miwa. It turns out Satoshi and Yuu are NOT half-brothers, and Yuu is so upset that he was wrong all this time that he professes his love for Miki, and they become a couple (hiding it from their parents).
When the family meets Chiyako’s brother Eisaku (actually, cousin adopted into the family), he casually admits he had a crush on his cousin Chiyako, and Yuu wonders if maybe he is his real father. But Eisaku informs Yuu that he was never involved with Chiyako; he kept his feelings to himself, so he can’t be Yuu’s real father. And just when Yuu decides to stop digging in his parents’ past, he uncovers some pictures of his and Miki’s parents from college. Already suspecting that his mom’s old boyfriend might be his real father, seeing that his mom used to date Jin before she married Youji, Yuu jumps to the conclusion that he and Miki share the same father and that they are half-siblings. He breaks up with Miki on Christmas Eve, but doesn’t tell her why. He just says it’s because he’s selfish and doesn’t love her anymore. In order to get away from his family and Miki, he enrolls in Kyoto Institute of Technology, but he can’t truly forget his love for Miki.
In the final issue, it is revealed that he and Miki are not biologically related, and they get back together.
Personality:
Yuu is a master at masking his emotions. His pretty face attracts a lot of admirers, and it makes for easy deflection of uncomfortable conversation. In 6th grade, he accidentally saw a letter written to his dad from his grandmother, that insinuated that his dad was not his biological father. He was devastated, but never confronted his parents about it. His only change in behavior was that he locked himself in his room and didn’t talk to anyone for about a month. It was during this time that he realized he should be grateful he has a father, even if they weren’t related. This is why he doesn’t talk back to his parents, or make any objections to their decision to divorce and swap spouses with the Koishikawas.
He can be rude to other characters, and doesn’t always answer their questions directly. This is because he is insecure and unsure if he can trust anyone. He wants to be an architect when he grows up.