I don't have enough context to determine exactly who 'garp' is. It could be a newly created character by the fanfic writer, or it might be a character from a relatively unknown story that is being incorporated into the 'ace fanfic'.
Honestly, I have no idea. The outcome for Carl could go either way. Maybe there are hints or foreshadowing in the recent comic issues, but I haven't kept up with them to know for sure.