So like, after reading the manga and watching the anime, I just need some time to process.
First things first: Haruki (brother), Kiriko (sister), Kiruko (brother + sister = MC)
It seems that Kiriko and Robin had some sort of history together before everything went to shit. In ch. 33, Kiruko had a flashback from Kiriko's POV where the dialogue says "Haruki always sleep really well/is a deep sleeper" and it's confirmed in the anime that Robin was the one who said this. This flashback is Kiriko's POV, and it looks like Robin and Kiriko were in the same room together while Haruki was sleeping next to them. This flashback was triggered after Kiruko got raped by Robin. And it seems that the body remembers sensations/has memories of the original person. So I'm speculating that Robin may have had sex with Kiriko before she died (whether it's consensual or not, we don't know).
On the other hand, I am speculating that Robin was the one who shot Kiriko in the head. When Kiruko found Robin again after 5 years, Robin expressed a shocked/scared face. Probably because Robin was surprised to see someone who he thought he had killed. Kiruko says that he can recall his sister's memories, and in ch. 33, Robin's face was shown next to a gunshot sound. And in the anime, the gunshot sound was associated with Robin's face as well. So it could be that Kiruko saw Kiriko's memories of being shot by Robin. In ch. 53 when Kiruko met Doctor Sakota again, the Doctor said "When she was brought before me, your sister had a bullet hole in her head." Anyway, we don't know what happened after Kiriko tried to save Haruki from the Man-eater... all we know is that Robin's gang is usually the ones who show up to deal with the Man-eaters. So it could be assumed that Robin and his gang came after the Man-eater who attacked Haruki, and some sort of altercation between Kiriko and Robin happened. Anyway, I'm just playing a guessing game at this point.
This topic may contain spoiler
So like, after reading the manga and watching the anime, I just need some time to process.
First things first: Haruki (brother), Kiriko (sister), Kiruko (brother + sister = MC)
It seems that Kiriko and Robin had some sort of history together before everything went to shit. In ch. 33, Kiruko had a flashback from Kiriko's POV where the dialogue says "Haruki always sleep really well/is a deep sleeper" and it's confirmed in the anime that Robin was the one who said this. This flashback is Kiriko's POV, and it looks like Robin and Kiriko were in the same room together while Haruki was sleeping next to them. This flashback was triggered after Kiruko got raped by Robin. And it seems that the body remembers sensations/has memories of the original person. So I'm speculating that Robin may have had sex with Kiriko before she died (whether it's consensual or not, we don't know).
On the other hand, I am speculating that Robin was the one who shot Kiriko in the head. When Kiruko found Robin again after 5 years, Robin expressed a shocked/scared face. Probably because Robin was surprised to see someone who he thought he had killed. Kiruko says that he can recall his sister's memories, and in ch. 33, Robin's face was shown next to a gunshot sound. And in the anime, the gunshot sound was associated with Robin's face as well. So it could be that Kiruko saw Kiriko's memories of being shot by Robin. In ch. 53 when Kiruko met Doctor Sakota again, the Doctor said "When she was brought before me, your sister had a bullet hole in her head." Anyway, we don't know what happened after Kiriko tried to save Haruki from the Man-eater... all we know is that Robin's gang is usually the ones who show up to deal with the Man-eaters. So it could be assumed that Robin and his gang came after the Man-eater who attacked Haruki, and some sort of altercation between Kiriko and Robin happened. Anyway, I'm just playing a guessing game at this point.
I'll continue waiting for updates.