Ask Lemmy

People have given some good recommendations so far, but here's mine:

Dear Brother A classic girl's love story set in 1970s Japan, with a schoolgirl going to an elite private school, and falling in love with one of the school beauties, who is an absolute bad girl who takes pills and smokes. It ends sadly, but it is one of my favorite animated series.

Sailor Moon Classic 1990s anime focusing on a group of girls who transform into magical girls (named Sailor Scouts) who they can fight evil. Although it was originally censored in the U.S. at least, one of the key relationships, as the seasons go along, is between Haruka and Michiru, otherwise known as Sailor Uranus and Sailor Neptune. Both women are very in love with one another. Also, the final season features the Sailor Starlights, who are men in "real life" but when they transform, they become women. The protagonist, Usagi, is also a bisexual icon.

Revolutionary Girl Utena The two protagonists, Anthy and Utena, are undoubtedly queer (where they fall, as lesbian or bisexual is up to interpretation), with both coming to know each other after Utena finds herself involved in duels over the "rose bride" (i.e. Anthy). As time goes on, they become closer to one another, even though secrets and disturbing truths are revealed. There is some abuse of Anthy, and later of Utena, going on here, so be warned, but this is still a very good series. If you want to see something even more queer than this, then I'd recommend the 1999 film, Adolescence of Utena, if you have a chance to watch it as well.

Cardcaptor Sakura Along with featuring bisexual, gay, and intersex characters, the female friend of the protagonist, Sakura, named Tomoyo, is deeply in love with her to such an extent than she makes ALL of her battle costumes and films her during battle with her camera. This is such a classic series which was later continued in Cardcaptor Sakura: Clear Card.

Simoun A classic series with one side in ships which are only powered when two girls kiss one another. While there's certainly some issues with fa service and the like, over all, this series has a lot of women loving women.

Sweet Blue Flowers A wonderful series featuring various lesbian and bisexual characters. One of the protagonists comes out as lesbian in the fourth episode and begins a relationship with another woman. She later realizes she has romantic feelings for her female friend, who later reciprocates.

Whispered Words Another wonderful series, this one involving a high school girl who is in love with her female friend but does not want to act on those feelings. At the same time, her friend has feelings for her.

Adventure Time Through this series, a bisexual vampire woman dates a young male wizard and later begins flirting with, and ultimately has a relationship with, a candy princess. Their relationship was later expanded in the Adventure Time: Distant Lands (a spinoff/continuation) episode "Obsidian," with some great songs, with Olivia Olson voicing the vampire woman.

Steven Universe Created by Rebecca Sugar, this series follows a boy with a diamond in his belly, and his three guardians, who are Gems, who come from another world. It's later revealed that two of these guardians are in a "fusion" with one another, symbolizing their romantic bond. There's also various other queer characters, including pansexual, gay, intersex, and asexual characters.

Otherwise, I agree with the person who recommended RWBY. That's it for series over 10 years old. I have more which are more recent if you are interested.