What happened five years ago hasn't been unveiled yet. I have a few theories....I believe Robin, in trying to rescue other people, may have put himself, and thus Seo Jin, in life threatening danger that nearly killed them. Or perhaps Robin, by playing hero in the fire, caused major suspicion that Seo Jin has multiple personality disorder. Another possibility is that Robin went into remission at a critical moment during the fire, leaving Seo Jin vulnerable and resulting in the death or injury of someone.
