??

I think the opposite. Ryan said the Christoph killed the culprit for poising him a long time ago. What if somehow Ryan's sister was the one who poisoned him and Christoph is her kid and she died giving birth to him? It would makes sense to say that Christoph "killed" the culprit. But I don know, I'm probably thinking too much since Christoph seems related to that man from the organization which took Kyon and Christoph on the past.

But Ryan was poisoned by the VS solution in Lucaon's mansion, together with Lucaon's parents. That happened ages after this story with his sister. Christoph was the one who gave the solution to a servant who worked by Lucaon's, he poisoned the wine, Christoph then killed the servant.

+ it was already explained what relationship exists between Itron and Christoph... did you even read the story? :D He is step-brother of the head of Itron, I forgot the name - Edwin I guess

I think what happened was Intron/Edwin manipulated Christoph to get the servant to poison the Selvoir family. At the table drinking the wine was also Ryan, along with his sister and her husband (Lucaon's parents). Christoph was ordered to kill the servant who poisoned the family by Edwin, meaning Ryan could not have any damage done to his core reversed by the remedy of the culprit conveying remorse, seeing as he has long been dead, and it is now that Ryan is no longer able to fight his weakened core and he is dying. Ryan wants to wipe Christoph's memories of his time with him, in order to protect him from the reality that he played a part in harming his beloved Ryan.

Yeah, I read it, but I forgot this

I read a lot of comics and mangas here, more than 100, and when they are not updated so frequently I start to forget the details. Sorry for being human