Part romance, part slice-of-life anime, Toradora! is built around the antics of two neighbors who become something more. When Ryuuji and Taiga actually come face to face in the anime, it's not initially as friends; it's more like disgruntled coworkers. When they agree to help one another turn their crushes on classmates into relationships, it's clear that they're going to be doing a lot of growing together over the course of the series.
In addition to Ryuugi and Taiga, however, Toradora! is populated by a colorful cast of their friends - and every so often, their parents. While not every character gets storylines devoted to them, they all have something to offer the audience. Whether they're entertaining comedic relief or wise beyond their years, these characters are the best of the show.
Haruta
Not a lot of attention is paid to Haruta in the early episodes of the anime's single season. He largely blends in with the rest of Ryuuji's class. At about the halfway mark, however, his personality gets a bit more fleshed out and he starts to make appearances outside of just the classroom.
Haruta isn't often taken seriously by his classmates thanks to his class-clown nature. He does provide a bit of levity for the audience though. So much of the series becomes dramatic and emotional, so any time Haruta is present in the story, the audience knows they're in for a few laughs. He's a great character to break the tension.
Kihara
One of the popular girls, Kihara is a sweet teenager. She's just trying to get through school and live her best life. That includes attempting to become closer to her crush Kitamura. Unfortunately for Kihara, her crush happens to be the same as Taiga's.
The audience doesn't get to learn a lot about Kihara as her efforts to get close to Kitamura are often thwarted by Taiga or Ryuuji. It's refreshing when she becomes more than just the quiet girl trying to get someone's attention by the time the class ski trip rolls around. She and Noto get into one serious argument, and the audience likes her just a bit more as a result.
Noto
Because Noto spends so much time in the background or paired up with his friend Haruta in scenes, he doesn't really exhibit his own character arc in the anime. The audience does, however, get to see him slowly fall for Kihara, though he never actually admits it.
The closer Kihara tries to get to Kitamura, the more hostile Noto becomes with her. The strange tension between them boils over in one of the most memorable scenes that's not actually about one of the main characters. They get into a yelling match on the class ski trip, and the audience gets to understand them a little more. Sadly, the audience also never finds out if Noto admits his feelings or if Kihara ever realizes that he likes her as more than a friend.
Sumire
Toradora! takes its school politics very seriously. The student body president is treated with the utmost respect by everyone except for Taiga. Though much of her work is done off-screen, it's clear that work is incredibly hard as she makes sure every school event goes off without a hitch.
Sumire initially appears militaristic in her approach to other students. Eventually, her softer side is shown as she rejects a potential romance with Kitamura. She cares for him, but Sumire knows she'll only break his heart in the long run as she has serious ambitions and is leaving to study in another country. Sumire might not be everyone's favorite character, but she's thoughtful and pragmatic, and the audience can't fault her for that.
Yasuko
Yasuko is a sweet woman who cares very much for her son and his future. She works incredibly hard, even taking on multiple jobs at one point because she wants to pay for Ryuuji to go to college without him needing to worry about the money. Yasuko means well, but she doesn't always come across as the most caring.
She relies heavily on her teenage son to care for her; it's almost like she forgot how to parent somewhere along the way. Yasuko also doesn't often take responsibility for her actions, but she tries very hard to be better for her son, and that makes her intensely likable for the audience.
Kitamura
Kitamura is a nice guy. He's athletic, well-liked, active in school organizations, and always tries to be there for his friends. Initially, he seems like too much of a nice guy when someone as antagonistic as Taiga is nursing a crush on him.
It's a little hard to fathom that most of the hidden feelings in the series are centered on Kitamura too. Kihara, Taiga, and Sumire all have a crush on him, though the degree of the crushes varies. He's not as compelling of a character as some of his classmates, but he is incredibly supportive of the people around him, and for that, he earns a spot right in the middle of the best characters.
Ami
Ami is not a nice person, though she hides it well. She doesn't outrank Kitamura because she's a good friend. She outranks him because she's the more interesting character to watch.
Ami is going through a lot. She's a model who puts her career on hold as the result of being stalked, she and Taiga immediately don't get along, she develops feelings for Ryuuji, and she's the most observant person in her friend group. As she slowly starts to reveal her true nature to those around her, Ami becomes closer to Taiga, even singing in a holiday pageant with her. She's the first to actually know how everyone around her feels about everyone else, proving herself much wiser than the other teens, even if she still plays childish games with other people's feelings.
Minori
Taiga's long-time best friend, Minori is like the more excitable version of Kitamura. Perhaps that's why she's initially Ryuuji's crush. She gives everything her all - all the time. Some might even accuse her of distracting herself with jobs, activities, and sports so that she doesn't have time to be unhappy.
In any other anime, Minori might even be the protagonist. Her character development is just as complex as the two main characters as she's there for every step of their schemes to get their crushes. Minori is often the subject of the schemes as Taiga tries to make her and Ryuuji closer. Minori surprises everyone, however, with her brief moments of darkness and doubt, revealing how introspective she can be.
Ryuuji
Much of the anime's story is told from Ryuuji's point of view. As a result, his growth is usually most obvious to the viewer. After all, he softens to Taiga right away, agreeing to help her even after she breaks into his apartment.
He's one of the most well-rounded characters in the series. His obsession with cleaning stems from how disorganized his mother is. His desire to help Taiga is partially a result of understanding how it feels to be judged based on your appearance. Ryuuji slowly falls in love with her, and though it takes him longer to figure it out than it takes the audience, it's still fun to watch.
Taiga
Taiga might not be a magical girl, but that doesn't mean she isn't incredibly strong and capable of seemingly impossible feats. Kicked out of her dad's house when they didn't get along, Taiga has her own apartment - that Ryuuji ends up cleaning for her. She's sloppy and reckless, but most of all, she's incredibly socially awkward.
Taiga wants to make friends, though she won't admit it. She also wants to find ways to express herself that don't involve hitting people. As she falls for Ryuuji and becomes friends with Ami, her temper calms a bit (though never completely) and she regularly puts others before herself. She is a mass of contradictions as she's just as likely to scream at someone about their childish ways as she is to be in awe of a holiday celebration. All of her different personality traits could make for a messy character, but instead, they make her feel real, despite the dramatic nature of her story.