Tatewaki Kuno is a prominent supporting character who serves as both a rival and an unrequited suitor. He is a senior at Furinkan High School and the captain of the school's prestigious kendo club, a position that reflects his skill as a master swordsman. Coming from a wealthy and distinguished samurai family, Kuno is deeply proud of his heritage, which he believes sets him above others. This background shapes his core personality; he is supremely arrogant, bombastic, and speaks in an overly formal, flowery, poetic manner that he considers befitting his noble status. He has given himself the grandiose nickname The Blue Thunder of Furinkan High, a moniker that, along with his immense ego, leads him to be supremely confident in his abilities despite suffering near-constant defeat.

Kuno's primary motivation is his delusional and obsessive quest for love. He had long been publicly infatuated with his underclassman, Akane Tendo, even instituting a rule that any boy wishing to date her must first defeat her in combat, a decree that forces Akane to fight off a horde of suitors each morning. His role in the story becomes more complicated after his first fight with Ranma Saotome, Akane's fiancé. When the two fell into a pool and Ranma transformed into his female form, Kuno was defeated by the mysterious pig-tailed girl and instantly fell in love with her as well. This event solidifies his central role as a comedic rival. He now pursues both Akane and the pig-tailed girl with equal fervor, genuinely believing that a man of his stature deserves to have them both. A key element of his character is his complete and willful ignorance regarding Ranma's dual nature. Despite witnessing Ranma transform on multiple occasions, he refuses to accept that the boy he despises and the girl he adores are the same person, instead concocting elaborate fantasies involving black magic and mind control to explain the situation.

His key relationships are defined by his obsessions and rivalries. He views Ranma Saotome as a dishonorable sorcerer who has somehow enslaved the pig-tailed girl, making him Kuno's most hated enemy. His affection for Akane is unreciprocated, as she finds him to be an annoyance. He also has a complex and competitive relationship with his younger sister, Kodachi, which is marked by a strong sibling rivalry and frequent, elaborate schemes against one another. One of his most notable interactions is with Akane's middle sister, Nabiki Tendo, who is his classmate. Nabiki frequently manipulates his obsessions for profit, selling him overpriced, candid photographs of Akane and the pig-tailed girl, a scheme Kuno never sees through. In terms of development, Kuno remains a largely static character, defined by his unwavering arrogance and delusions. While he is humiliated and defeated time and again, primarily by Ranma and Akane, he never learns from these experiences nor gains any significant self-awareness, serving as a reliable source of comic relief throughout the story.

As a fighter, Kuno is a genuinely skilled martial artist, specifically a master of kendo, and was considered the strongest student at Furinkan High before Ranma's arrival. He is never without his bokken, a wooden practice sword he wields with great speed and precision. His signature technique involves thrusting his sword at high speeds to create razor-sharp air pressure that can shatter stone, an attack he often calls the Blue Thunder Strike. On one memorable occasion, he developed a nearly invincible spinning technique to slice watermelons, which proved to be a challenge even for Ranma. However, his abilities are severely hampered by his massive ego and his refusal to acknowledge the strength of his opponents, which often leads to his swift and comedic defeat. Furthermore, he is almost entirely reliant on his sword and has little to no skill in unarmed combat, a weakness his enemies frequently exploit.