I watched Kara no Kyoukai first (both regular order and in chronological order). All of it, including the epilogue and remix. It was visually amazing and had an intriguing storyline. It all made sense to me, at the end, but I can’t help but think there are holes that could be filled, things left to be explained. So… I hunted down the original, Empty Boundaries, the light novel for this series, translated here. The light novel version is quite interesting. It is told from different perspectives in each section. Mostly, it shifts from Mikiya to Shiki, but it also has perspectives from other characters too. Because of this, you understand the characters in the story a lot better than if you only watched the movie series, which is told from a third person perspective. And I have to say ufotable did an amazing job at the movies. The movie is adapted from the light novels, and retold in a third person perspective. It has all the implications from the light novel, meaning you feel the same as if you were reading the novel.
Here are some things I found in the light novel that is left out/was not explained (will be updated as I read further):
Note: Shiki refers to the female one while Shiki refers to the male one.
When Shiki was at the scene of crime in front of her house and Mikiya happened to be there, Shiki‘s consciousness went in and out, possibly because Shiki switched control with her throughout the scene. Shiki admired the blood flowing down the stones, but she does not have much recollection of the motherly smile she did in front of Mikiya, or even how she really ended up there. Because of the scattered memories, Shiki had assumed that she was a murderer. When Shiki tried to ask Shiki about the event, he doesn’t answer her. Then…when Shiki and Mikiya had the conversation at the rooftop for the first time after witnessing the event, it was told in Shiki‘s perspective. Shiki‘s personality came out in the middle of the conversation when Mikiya was avoiding to talk about the conversation. As Mikiya was saying that he didn’t actually see anything and ultimately, he wanted to believe her, Shiki was touched, because Mikiya was trying so hard to lie and conceal his true feelings of her. However, on the other hand, Shiki wanted to kill him, even though Shiki never wanted to. From what I understand, Shiki has taken a liking to Mikiya at this point, but it conflicts with her original existence. He showed her a world that she had longed for, a normal peaceful life. Also, from what we know from the movie series, Shiki‘s existence is “denial” while Shiki‘s existence is “affirmation.” When Shiki finally decides to stop ignoring Mikiya and has that talk in the classroom bathed in sunlight…this part was told in Shiki‘s perspective. Mikiya confessed and Shiki was touched by his naivety. She said that “those words which are probably just nothing to him are the most that anyone has given me; happiness, and my destruction, in one sentence.” He was breaking her out of her shell, but at the same time, she realized that if she were to get close to anyone, Shiki would kill that person. Mikiya was pulling Shiki away from her own abnormal world. Because of this, Shiki wants to kill Mikiya to protect their world from being deconstructed by Mikiya.