If you have read the Tokyo Ghoul manga or watched the Tokyo Ghoul anime, you will see that the series ended with a cliff hanger: in the middle of an epic battle, no one has won, no one has lost, the final transformation is not yet revealed. It just ends, leaving all of us baffling, the way the Monster Musume no Iru Nichijou Manga did.
Thankfully, the first thing the author does in the sequel series Tokyo Ghoul A is finishing this thing that keeps dragging in our mind for months and moths. However, he also decided to end it on loose ends. The cliff hanger turns to the event that Kaneki, who was brutally tortured by the villains, chose to join the villains, leaving the ones that came to love him behind. Now that is what I call a twist.
Clearly, the hero in this series is Kaneki, but in the sequel series, the author has decided to make it the battle of two sides, instead. The people Kaneki has left, and the police who are going after the ghouls. It was not just angst anymore.
Toka was Kane's love interest. Seeing him disappeared, the girl decided to restructure her life completely and mimic Kaneki before his disappearance (if you find this familiar somehow, then it was also in the Harry Potter books in order). She tried to get into his university, she takes care of Hinami the orphan ghoul who he used to adopt, she wants to be friend with Kaneki close friends. We are not yet to understand why she changes her life to such extent just to be closer to him. A theory is that she hopes to understand why then the man turns into the dark side. Unfortunately for us, the anime did not explore these motivations. We only see this confident girl transforming herself into an angsty teenager who keeps crying over the prince that has left her, and does not want to do anything about it.