Stop!! Hibari-kun! is a manga (comic book) which ran from 1981 to 1983. It was animated in 1983 as a 35 episode television series. The plot is relatively simple, a boy named Kousaku is left parentless when his mother dies after a long illness (his father had died years before) and goes to live in Tokyo with a friend of his mother's, Ozora Ibari. Ozora Ibari is a yakuza (organised crime) clan head, and has four children. All appear to be beautiful young women, but most beautiful of all is his classmate, Hibari, with whom Kousaku promptly falls in love. It is then revealed that Hibari is actually male and the very reluctant heir to the Ozora clan.
If you predict that Hibari's gender identity is played up for laughs, you would be right. If you predict that because of this fact Hibari is the butt of the jokes, then you would be very wrong. This is where Stop!! Hibari-kun! departs rather drastically even from so-called "genderbending" or "otokonoko" manga and anime being created today. For the 1980s, and for Shonen Jump especially (an anthology known more these days for Naruto and Bleach and One Piece than it is for progressive, if comedic, portrayals of sexual minorities in Japan), this narrative is incredibly surprising.
Having watched the series and read a large part of the manga, Hibari's gender identity is definitely "girl." I tend to use female pronouns for this reason. She doesn't tend to argue with having male pronouns applied to her, but that is only when she is facing situations with her family or with Kousaku. In her daily life (which largely centers around her school and social lives), Hibari is entirely stealth. Afraid of what might happen if Hibari's assigned sex were to be found out, her sisters and retainers aid her in her gender expression. Her friends, classmates, and teachers are completely unaware of her assigned sex (although a few antagonists have their suspicions).
Although overt slapstick comedy, the series does touch from time to time briefly and subtly on issues of Hibari's gender dysphoria and the physical aspects of her experiences. There are clear cues that Hibari is displeased with the male aspects of her body and is upset by the reality of female puberty passing her by—and male puberty possibly catching up with her eventually. Although brief and subtle, so much so you could miss them if not paying attention, these glimpses into Hibari's mental states are incredibly nuanced for a work of its time, genre, and anthological home.
The real strength of the series can be found in the fact that rather than Hibari's gender identity being maligned comedically, it is the other characters attempts to cope from which the humor is derived. Hibari's gender is never the joke. The major source of humor is in Kousaku's inability to deal with his clear attraction to Hibari. His distress is really of his own making, because even if his sexual orientation is straight, Hibari is a girl, so there is nothing not straight about his attraction. The joke isn't on Hibari, it's on Kousaku because of his cisheteronormative paradigm. A secondary source of humor is other characters' reactions to Hibari, and their attempts to change Hibari's gender identity end in spectacular, hilarious failure. The joke's on them as Hibari changes not at all.
Watch the first episode subtitled by fans here: