With how much Kafka means to Reno (ch 101), also being his love interest (Understanding Reno & his bonds)...
...and how Reno reacted when he thought Kafka is about to get killed (by Hoshina) (ch 19 / s1e7(?))...
...and then how dejected & determined to become stronger he became after Kafka was captured (ch 34 / s1e11(?) & 62 / s2e7)...
...how profoundly guilty he felt for not having been strong enough to protect Kafka and Iharu (ch 62 / s2e7)...
...it makes one wonder what would emotionally happen to Reno if Kafka at some point died. And not just at all but specifically in a way that would make it remotely understandable for Reno to blame himself. Or what would Iharu dying like that do to him. He likely wouldn't become morbidly obsessive, given he doesn't spiral when Kafka is captured + he seems an earned-secure type. But it could potentially influence his ability to control his desire for power in order to protect, in the context of using No. 6. Maybe he'd struggle with losing himself, again, and Iharu would have to save him again.
(Afair, Kafka hasn't suffered the exact kind of personal losses as did Reno; maybe if he did, his relationship to killing kaiju & protecting his loved ones would be about as intense as Reno's. Then we have e.g. Narumi, whose past is very similar to Reno's (explored in b-side), & his dedication to fighting kaiju seems closer to Reno's. Personality definitely plays a role, though, so those with the same kind of experiences don't grow into the same kind of people).
Iharu has almost experienced that exact kind of situation (ch 17 / s1e7).
Which makes one wonder how he would have carried on if Reno did end up dying there. He'd probably feel immense guilt as well, having tried to protect him (even if the motivation might not have been entirely selfless). Perhaps even shame, given his insecurities around killing kaiju.
It would have been interesting to see whether that moment has left a scar, or has Reno ending up okay entirely patched up any guilt or feeling of failure he might have had.
Either way, with Iharu being Reno's only other close friend, he'd probably step in if something like that happened to Reno. Similar to how he tries to humor him in ch 34 / s1e11(?).
And then the anime expands on that a tiny bit, in s2e1. https://www.tumblr.com/neverstopwoandering/797850093652983808/the-anime-extra-scene-in-s2e1-with-iharu-pulling?source=share.
After what happened during their first mission (again: ch 17 / s1e7), Iharu does understand what kind of emotional turmoil Reno would be going through; what kind of emotional turmoil Reno has gone through.
He might seem like a brash goof, but scenes such as his self-reflection during Reno's No. 6 arc (ch 60 & 61 / s2e7) or the phone call with Kafka in ch 67 / s2e9 demonstrate he really is emotionally intelligent. Even if his competitive side can make him come off as abrasive at times (e.g. how throughout half the series his primary motivation seems to be to beat Reno. Though he still drops that when it matters & helps him however he can. And he is self-aware about it (ch 60):
Iharu is honest, not just with others but also with himself), or his extroverted personality can sometimes get in the way & make him look silly or inconsiderate (e.g. how he greets Kafka in ch 129). People have layers.
Either way.
It seems tentatively more likely for Reno to die sooner than Kafka or Iharu, though, given he's the No. 6 user. If he is indeed intended to die young then at least he's gotten to find people he became close with. We can only assume — based on his current personality & behavior — what his life had been like before he met Kafka; maybe fairly lonely. Regardless, it seems that finding those two joyful guys (the two leos of kn8, too. I'm not into astrology but it does seem that the author chose their western astrological signs intentionally, looking at how all different characters fit their own. Fun fact: with Reno, Iharu and Kafka make the fire trio of kn8, since Reno is an aries) is what he's been needing. (ch 64 / s2e8, ch 22 / s1e8(?)).
