Nekomonogatari (Kuro)

This is the story of Hanekawa Tsubasa, a friend of Araragi's (his only friend before Bakemonogatari). The story of her family life and her inner conflicts is something that we all experience, but something about it makes Hanekawa special (supernaturally, of course). Nekomonogatari Kuro explains her motives in Bake and concludes in the Nekomonogatari Shiro arc, which takes place in Monogatari Season 2. Her story is so heartbreaking, and this series is a must for anyone watching the Monogatari series. Hanekawa's tragedy plays out through Monogatari and this little spinoff explains it all.