Taiga is a girl in Ryuuji's class. She has a well-regulated and beautiful appearance though is unable to stomach company from others. Due to her often snapping at others in brutal ways and her short stature, she is given the nickname "Palmtop Tiger." Her under-developed body and the added nickname has given her a complex which in turn serves to give her a negative attitude and facial expression. Essentially, Taiga gets upset easily and is considerably clumsy. She is also brutally honest, typically when she is lashing out at someone. Due to her cute looks (described as a doll by Ryuuji), she often gets confessions of love by boys, but she turns down every one of them, including Yuusaku Kitamura (which she later regrets). Despite coming from a well-to-do family, her life with them is very difficult because of various problems. Her father and mother got a divorce, leaving Taiga with her father. When he remarried another woman who was significantly younger than himself, it caused misunderstandings between Taiga and her step-mother. One day it became too much for Taiga, causing her to run away from home and since then, she has taken to living on her own. Since she came from a privileged household, she does not know how to do any domestic chores. When she meets Ryuuji and learns of his domestic talents, she ends up relying on Ryuuji to clean up after her. Aside from sleeping in her own house, and going to school, she spends most of her time at Ryuuji's house; so much so that she is considered a member of his family. At the beginning of the story, she is infatuated with Ryuuji's best friend Yuusaku Kitamura and gets nervous every time he appears around her. Ryuuji finds out due to a misplaced empty love letter from Taiga meant for Kitamura. Ryuuji then admits to having feelings for Taiga's best friend Minori. Due to this, Taiga and Ryuuji team up to help each other get into a relationship with each other's best friend.

Koyomi Araragi is a third year high school student who survived a vampire attack during spring break and barely regained his human life in the time that followed as a boy with remnants of vampiric traits. He can see in the dark, his eyes turn red when he gets angry, and he heals incredibly fast. As a result, he questions his lifespan. He remains scared of morning sunlight despite the fact that it no longer has any negative effects on him. Koyomi is a laid-back person whose only real friend at school is Tsubasa Hanekawa. He's a poor student, close to failing every class except math. It is revealed through conversations that he's quite knowledgeable with anime; a fact even noted by Nadeko Sengoku once. Although he is shown to be attracted to the other girls, he turns their advances down due to his loyalty to Hitagi. Other characters seems to speculate that Koyomi is a lolicon, particularly Mayoi and Hitagi, with Hitagi thinking that Nadeko is a "threat" to her. He is very noble, which is why Hitagi is attracted to him. He is willing to help others at the cost of his own life. As such, the female characters he has helped are quite attached to him. He feels most comfortable talking to Mayoi, Shinobu and, from the Second Season on, to Yotsugi about his problems. Koyomi is the only person who thinks that his family relationship is bad, with Karen and Tsukihi thinking otherwise. His parents were revealed to be police officers. His personality is portrayed more clearly in the novels, where his inner thoughts show him to be much more perverted and intelligent than the anime leads one to believe. Due to events prior to Kizumonogatari and Bakemonogatari, Koyomi avoided having friends and seemed to have lost faith and trust in people and himself. (Source: Bakemonogatari Wikia, edited)