-The initial flashback in the novel was placed after Oshino wakes Black Hanekawa. Concretely that part was detailed only about the dialogue between Araragi and Hanekawa. It was mentioned in passing Hanekawa buried a cat which has been run over by cars, and in other chapters it was mentioned that Shinobu had some kind of role in the resolution. Shaft had to invent half of the flashback (I must say the picture of Black Hanekawa by Vofan was misleading). Also in the novel it was specifically mentioned Hanekawa's gauze was covering the whole left half of her face. Shaft got it wrong, I don't know if intentionally. Anyway, the gauze being big was supposed to be the point, otherwise it could be easily explained with an incident. It had to be obvious someone hit Hanekawa.
-Even in the novel it was not properly explained how Oshino managed to tie up the cat. As soon as the flashback finished the cat got caught.
-I thought the date with Senjougahara was complete enough since a whole episode was dedicated to it, but Shaft actually cut many lines here and there. And the car was a Jeep (which Senjougahara's father borrowed from a friend). The chapter has been translated on Bakatsuki so I will just point out a couple of things.
-From Araragi's point of view, Hanekawa and Senjougahara have both high grades so they are grouped together, but Senjougahara replied that Hanekawa would group her with Araragi instead. Hanekawa is the real thing (this theme was carried on in Nise).
-When Senjougahara learned Araragi was getting along nicely with Kanbaru, she stated she could use her as a hostage, because Kanbaru obeys her in everything. She was making threats like "do this or Kanbaru will walk the school on four feet with her bottom bare. Why do they always cut the best gags in the anime?
(by the way, Senjougahara said she would get her body ready by the next week!
)
-Senjougahara calculates things so that she arrives at school perfectly on time.
-Hanekawa in the park was actually wearing her coat (not just draping it over her shoulders), a thin coat with long sleeves and a long hem. Araragi could just understand she was wearing pajama pants underneath. He was thinking of strategies like in the North Wind and the Sun fable to make her undress. Later, when he met Black Hanekawa the second time for some reason she had taken out the coat.
-While going to Oshino with Hanekawa sitting behind him on the bike, Araragi was enjoying bumps on the road a bit too much, so at a certain point Hanekawa squeezed him. Araragi asked if it was the sumo technique of sabaori, but Hanekawa replied that that sumo technique is used from the front and its purpose is to target the opponent's knees, not destroying internal organs (Hanekawa trying to destroy internal organs... so HNNNNGGG
). Araragi was thankful Hanekawa didn't notice her cushions were softening the blow
-I don't know the reason, but the scenes of Araragi calling his friends to help him find Shinobu and the climax with the cat were all part of the same chapter. An 80 pages long chapter.
-The part with Kanbaru was considerably long considered the urgency of the matter. And Kanbaru was supposed to run at full sprint, altough in the anime we just see her walk. EDIT: according to Kanbaru, Senjougahara boasted on the phone about her date with Araragi for 5 hours (how much did Senjougahara sleep that night?). Kanbaru complimented Araragi, but said he hadn't won yet.
-Senjougahara said there was so much work to do about the school festival it was a waste of precious time even answering the phone. She didn't know how Hanekawa could manage it. By the way, at first she didn't even plan to answer the phone, she checked who was the caller just because the phone kept ringing.
-The scene with Oshino waving his hand at Araragi is anime original, as is the scene of Senjougahara working on the festival.
-In the novel it is just said Araragi kept circling around for hours, without eating, drinking or resting.
-EDIT: I was forgetting this. After Araragi experimented the energy drain, Black Hanekawa made him an offer, he could have touched Hanekawa's cushions in exchange for 1 dried bonito. Or 1 matatabi (cat powder). Or 1 Cat Food can. Araragi retorted it was as if the cat could only count up to 1.
-The Sawarineko has the trait of never coming out by itself. Its brainpower of an average cat merges with the knowledge of the host, and that creates Black Hanekawa. Even defeating Black Hanekawa, the Sawarineko remains in Hanekawa's heart.
-The purpose of Black Hanekawa is helping Hanekawa get rid of her stress at all costs. For this reason Black Hanekawa collaborated with Araragi finding Shinobu.
-Hanekawa was especially careful in hiding her feelings, but she appointed Araragi as deputy class rep exactly because she wanted to have him closer to her. And Araragi was just thinking she wanted to rehabilitate him! (damn his persecution complex!) By the way, Hanekawa persuaded the class by saying that "putting people in places of responsibility make them grow".
-This part was cut although it was very important. Hanekawa never thought Araragi would have been kind to everyone. She wasn't making a move because she wasn't thinking he would find another girl to help. That's why she kept telling Araragi Senjougahara could have liked better if he was not kind to everyone, she was drawing upon her own personal experience.
-There is a sub that translated the thing simply with "ask him out", so it's better to reiterate the point. Hanekawa's character wouldn't allow her to
steal a boyfriend. The problem was that Hanekawa's relationship with Araragi had become an illicit love, because Senjougahara had already made her move. That was making Hanekawa feel guilty, to the point she would have rather preferred if it were all due to vampire charm.
When Araragi revealed he couldn't understand Hanekawa's love pain, the cat remarked that maybe he didn't really love Senjougahara, he was just letting her have her way with him, and therefore it wouldn't matter if he switched girlfriend. Here Araragi would have got angry if he wasn't facing Hanekawa. Anyway, the cat was right
mostly it was just Senjougahara having her way with him
And I personally think it was a bit hypocrite to complain Hanekawa was giving in to her weakness because she resorted to the cat. After all even Senjougahara resorted to a kaii, and even her attacked innocent people at times
-EDIT: Incidentally, the cat says Araragi had a part even in the birth of the first Black Hanekawa.
-The fight with the cat was vastly revamped from the novel. The cat didn't strangle Araragi for example. In the anime it looked very cool though.
-It is a bit redundant to explain this, but it's better to state it clearly. As mentioned before, the cat acted with the sole purpose of reducing Hanekawa's stress. The fastest way was to have Black Hanekawa dying, so she was trying to get herself killed by Shinobu. If it really came to it though, she wouldn't have minded even directly killing Araragi. It was still an option for her. By the way, despite the acrobatics of Shinobu in the anime, if Black Hanekawa really meant to she would have dodged any blow, she was too fast for Shinobu.
-Hanekawa said the last lines while half sleeping, or possibly while Black Hanekawa's consciousness was still mixed with hers, anyway she was completely honest. By the way, the last thing she said was better translated with "Get your things straight". And since Hanekawa's training was not for show, Araragi was able to reply immediately.