Nisemonogatari

If Koyomi Araragi thought his life couldn't get any more complicated after meeting Hitagi Senjogahara, Mayoi Hachikuji, and Suruga Kanbaru, he's sorely mistaken.

Without any knowledge of how it came to be, Koyomi finds himself in an unknown place as a prisoner. The reason for and answer to his predicament seem to lay in Hitagi's past and the con artist Kaiki Deishuu, but it becomes clear that there's much more to it than that, and it will threaten the well-being of those Koyomi holds dear.

The second story arc of Nisemonogatari focuses on Koyomi's sister Tsukihi. When Koyomi meets a pair of enigmatic women who know suspiciously too much about him and his friends, he couldn't have anticipated the ramifications of their presence. Now Tsukihi's life may very well be at risk, and the cause behind it will shake the foundation of everything Koyomi knows about his sisters.