I think so too. Ruediger bounds to die, so Luca, fearing the heartbroken lovely aunt he has now, is afraid of Judith's breakdown when that happened. Ruediger will dies because his essence doesn't change, meaning he is willing to die for Luca (and now Judith)!
If I remember a comment from an earlier chapter, Ruediger is normally extremely focused on his duty, hence the comment on his essence never changing (and Luca revealing that he knows that Judith isn't the original) and how he'll just hurt her.
Personally, I think he's partially wrong mainly because of one reason alone. Judith
Remember, Luca has lived this life at least once, potentially several times already. Nothing has really changed...
except Judith herself because she is an out-of-context problem in and of herself. Judith not only surviving, but befriending and falling for Ruediger has created a scenario that likely wasn't in any of Luca's previous experiences and throughout the story we see him genuinely caught off guard with interactions between the two of them.
Luca is stuck with the information he knows and Judith is stuck with her increasingly less useful knowledge of the story. Both know mostly what the other characters will do based on that knowledge, but they both originally failed to realize how changes in the others behavior would affect outcomes of the other.