I just posted a bit from ACT 4, scene 6 wherein I posited that the real romance in this play is between Hamlet and Horatio. This moment supports that theory pretty strongly. It is very extreme for Horatio to suggest that he will die with Hamlet, especially when Hamlet has specifically just asked him to live and tell his story. It gets suddenly Romeo and Juliet-y up in here. Horatio doesn’t explain why he thinks he should follow Hamlet to the grave. Maybe it’s not that he loves him and doesn’t want to live without him – maybe it’s just some weird self-sacrificier, sense of duty or maybe it’s a kind of death contagion – like, everyone’s dying, I don’t want to be left out.
Love feels like the most obvious answer – though Horatio really is a pretty blank slate upon which to project. This is the most action we’ve seen from him the entire play and it seems very out of character from whom we’ve seen. Like, mostly Horatio just goes and looks at things, listens to people, receives letters, delivers letters and just generally doesn’t get involved. Suddenly he’s doing something and it’s dramatic and extreme. He’s either threatening or offering to kill himself with the poisoned wine. It’s a giant gesture either way, especially for a man who’s mostly been standing around observing.