The melodramatic king of Ouran High School's one and only Host Club.
Tamaki was born to a French mother and a Japanese father, to the great disapproval of his paternal grandmother, who forced the parents to separate. Tamaki lived with his mother as a child until she became too ill to care for him. In exchange for financial assistance for his mother, Tamaki made an agreement with his grandmother to come to Japan and become the heir to the Suou conglomerate and never see his mother again. In spite of this sorrowful past, Tamaki is an exuberantly cheerful, if often naïve, fellow. He began attending Ouran High School in middle school and became friends with Kyouya Ootori, pushing Kyouya to not simply accept his lot as the youngest son but to work hard and try to achieve something better. Kyouya often feels irritation at Tamaki's antics but accepts them.
Tamaki came up with the idea of creating a Host Club when he was in middle school and began seeking members, although he knew the club wouldn't be able to start until high school. As such, he established himself and Kyouya, then first-year high school students Mitsukuni Haninozuka (Hunny) and Takashi Morinozuka (Mori) as members of the club. He was eventually also able to conscript the Hitachiin twins, Hikaru and Kaoru, a year younger than himself, into joining the club when they joined high school. Each of the stories of Tamaki's winning over of the club members features Tamaki offering the others a chance to assume their own identity, separate from what's imposed upon them by the other people around them. The exception to this is Mori, who simply followed Hunny as he always did.
"Exuberant" is the defining word of Tamaki's existence; he never does anything half-heartedly. This extends from the Host Club, which often holds themed days with extravagant costumes and sets, to times when he feels pouty, when he will actually curl up in a corner of the room and sniffle. He almost never thinks badly of anyone or anything else, although he has a flair for the dramatic that sometimes makes him think that the worst has happened (such as when he couldn't get in touch with Haruhi Fujioka over one break, and he assumed that she and her father had been taken by the yakuza over a debt).
In spite of his naivete, Tamaki is extremely intelligent, often one of the top students in his class. He wishes above all to be himself, telling Haruhi that he is Tamaki before he is a member of the Suou family. His role as a host is that of the charming prince or king, sweeping the girls off their feet with romantic gestures that are, in the end, meaningless. He does have feelings for Haruhi, however, he's only just become aware of them in the manga.