Monogatari S00 E06 Nekomonogatari Kuro: Tsubasa Family (1)

Koyomi Araragi begins the day by being rudely awoken by his sister, Tsukihi. He decides to discuss love with her, asking how one can tell if they are in love or not. It turns out that recently, he can't stop thinking about his classmate, Hanekawa Tsubasa. Later, he runs into Hanekawa, who reveals a shocking fact which he may not tell anyone else about.