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)

Yuno Gasai is obsessively in love with Yukiteru (Yandere) as one can safely guess from just the simple name of her future diary. Yukiteru's condition and actions are recorded every ten minutes in her "Yukiteru" diary, it also provides small commentary made by Yuno in some of the entries. Its most obvious weakness is that it does not show Yuno's future at all—her condition, situation, or surroundings—unless it somehow involves Yuki. Working with Yukiteru's "Random Diary" diary, however, covers both of their diaries' individual flaws; as it has been said the two make for a perfect combo. Smart, beautiful and diligent—those who don't truly know Gasai Yuno would simply see the model student role she plays while at school. She is secretly obsessed with Yukiteru and would do anything within her power to assist him. She can be quite clingy and is highly fond of stalking him. When obstacles arise that either endangers Yukki's life or threatens their relationship, her thoughts turn murderous and she lets nothing get in the way of her path. Yuno is also able to quickly analyze and adapt to unexpected situations that may arise, and she puts thoughts into action without hesitation, performing what needs to be done without ever losing her nerves. These traits make her one of the strongest players in Deus's game, despite having one of the weakest diaries for providing self survival aid. And while Yukiteru is credited for triggering the greatest shift in future occurrences, Yuno is the one who has created the largest influence in those events. Yuno tends to carry around a box cutter with her at all times, though she will make use of other weaponry such as kitchen knives, hatchets, etc, when required. She is named after Juno (pronounced yu-no in Latin), the Roman goddess of Motherhood and Femininity.