For the first few pages I had a thought: “this feels like a death flag” but then I immediately dismissed the thought as just paranoia from being so anime-brained. In any other series that would have been fine but I made the mistake of forgetting who the author is.
The only thing that gives me hope is that the manga is nearing the end and Ruby dying (or going into a coma or something) would be the dumbest decision narratively and would utterly ruin the story. But I try to avoid thinking from a meta perspective.
Maybe Aqua will successfully save Ruby and tie up his guilt from failing to save Ai, and they just arrest the attacker instead of having another revenge arc.