Kaguya-sama: Love Is War is one of the hilarious romantic comedies airing this season. But this endlessly funny anime is more than just a series of gags. It manages to be a gloriously entertaining comedy while simultaneously telling a well-executed romantic story, and this brilliant feat is only achieved because of its near-perfect cast of characters, each playing off of the others in ways that progress both the comedic sequences and romantic plotlines of the series.
Kaguya-sama wouldn't have worked as well as it does if it without its meticulously-crafted character dynamics. Each character in the series has a unique personality and no two characters interact in the same way as they do with others. This, in turn, not just leads to fresh comedic situations depending on the characters involved, but also contributes to the character development of the main cast.
Take the titular character of Kaguya Shinomiya. Kaguya has a duality in her personality. She has an "Ice Queen" persona due to her emotionless upbringing by her father but also wants to become a more caring human being and learn to get along with others. These internal contradictions make her a very interesting character already, but the series takes it to another level in the way it uses the various aspects of her personality to create different relationships with her student council members -- for both comedic and character development purposes.
Kaguya is often shown to be ruthless and cold towards Ishigami, who initially believes that Kaguya wants to murder him. This is at first played to comedic purposes; however, as the series progresses their seemingly hostile relationship evolves to be one of tough love, wherein Ishigami learns to become less cynical due to Kaguya's believe in him, while Kaguya gets to inadvertently show the softer side of her icy persona.
The anime consistently does this with many of its other characters. Kaguya and Shirogane, who both have a crush on each other, try to make the other confess due to their competitive nature. This is of course played for laughs; however, their reluctance to confess also stems from their fear of vulnerability. And through character traits that were initially used for comedic use, the series develops their characters and progresses the romantic subplot in a sincere manner as the two characters learn to overcome their otherwise comedic character flaws.
Chika, on the other hand, is the wildcard amidst the various mind games Kaguya and Shirogane attempt on each other in their battle of confession. Her aloof, goofball nature is used to serve as a humorous obstruction to the main characters' daily psychological battles, allowing for the comedy to evolve with layered twists and turns. Depending on the character interacting with her, Chika's character traits are used to produce different effects.
When Kaguya interacts with Fujiwara, we see a more jealous, antagonistic and cold side to the former, whereas Fujiwara's interactions with Shirogane are used to flesh out Shirogane's weaknesses -- such as when Shirogane approached Fujiwara to learn how to play volleyball, in turn creating a comical mother-son bond between the two.
Ishigami is another character who is created specifically to work well in the group dynamic of the cast. He is often the only one in the student council capable of neutralizing Fujiwara's chaotic nature, in turn creating a third layer of comedy that can follow-up on the jokes Fujiwara's chaotic personality usually provides. Ishigami's personality is one that's cynical of people and society, which, just like Kaguya's personality, is mostly used for comedic intent. Though later on, through Ishigami's unique interactions with other characters, he learns to develop and improve as a character.
In the second season of Kaguya-Sama, we see a new addition to the student council, Miko Iino, who looks to be continuing the tradition of characters with two layers: comedy and character development. So far Iino seems to be an overtly innocent and uptight character with a suppressed deviant mind. This, as usual, is used as a comedic shtick wherein many jokes in the series are shown to end with her interrupting the main characters' shenanigans at the worst possible time, and assuming something dirty is happening before running away in embarrassment. Her uptight nature is also used to serve as a contrast to Ishigami's rule-breaking, uncaring personality, perhaps in an effort to progress Ishigami's character arc in the guise of a comedy routine, as the two opposing characters butt heads.
Kaguya-sama: Love Is War is brimming with such carefully-crafted character personalities and relationships, each serving the purpose of developing the plot and characters under the veil of comedy. This is how the series blends being consistently funny with a genuinely well-told romance story. The comedy and romance work together, and this couldn't have been done without its well-written cast and the meaningful way in which they interact.