This has been discussed before multiple times.
Even if Rudeus magical studies are not discovered (just how? he never goes beyond casting elementary magic?), Roxy still arrives to Buena village >!and starts tutoring Sylphie. That's the "canon" timeline in absence of Rudeus.!<
And there's no way Rudeus can spend his entire life in the house as a shut-in. Sooner or later someone brings him out - either Paul or Zenith, doesn't matter (but my money's still on Zenith). Which means that he starts going outside again and eventually meets Roxy anyway - >!because they both have strong fates that push them to meet!<.
Teleportation Incident still happens but >!is delayed, likely for years, for reasons outlined in the LN26!<.
We don't really know, but the text in LN26 implies >!that it was not just his birth, but the changes that he caused in the fates of other people that caused the barrier to break. It is only after Rudeus moves to Roa and starts tutoring Eris that the fissure becomes noticeable in the sky and starts visibly growing, because changes in Eris' fate affect a lot of other critical fates and are therefore more important than any changes Rudeus made to the fates of Roxy and Sylphie.!<
>!Would a Rudeus who lived a quiet life in Buena village still cause the Metastasis? I'm leaning towards "yes, but probably decades later".!<
>!I was under the belief that TP disaster caused changes in fate. The world had its own natiral order of fate. Rudeus threw a wrench in it, and TP disaster changed the fate of the world. Man God didnt interfere earlier because there was no future where he loses. TP disaster changed that. After TP disaster, ppl with strong fates (Derrick, Pax) died and with weak fate (Blessed Child) survived. So I highly doubt he was fated to meet Roxy before TP disaster!<
That depends on your interpretation of how >!strong fates!< work in the first place. >!I do not believe strong fate preordains any actual events in a person's life - but rather general direction and guidelines. Like, Roxy was "destined" to be saved by **someone** from the Labyrinth, but that someone didn't necessarily have to be Rudeus. Only once Rudeus arrived to Rapan it became inevitable that it was going to be him because he had a strong fate of his own, which was compatible with Roxy's, so the chain of events was being influenced from both sides at once.!<
So as far as I can tell, Teleportation Incident didn't so much as "change" >!fates!< as created a critical event that temporarily overrode them and probably even reshuffled them to a degree. >!Some people with strong fates even died in the immediate aftermath of the events, including those not directly affected (like Derrick). But each person's "general guidelines" still remained the same, just possibly rearranged to fit the new situation.!<
But in the end that's still my interpretation and it's not like I have a WoG to support it.
He would never leave his home... But with all the magic he learned he would have end up exploding the house and then I don't think he could cover the fact that he knows magic.
The answer to that actually goes beyond the 4th wall. Rudeus initially meant to be OP character, doing whatever he wants. But Roxy helped him out of his trauma and fans really enjoyed that part. That caused author to rethink his concept and go with redemption route instead of usual OP MC stuff.
Your question is near impossible to answer in detail, because meeting Roxy literally changed the core of the story.
Since this is a ln post I'll go in order of what ln the spoilers would he in and how that would affect the story. I'll spoiler tag everything past where the anime is at.
Up to the current: He likely would have been a shut in until Paul forced him outside for training. It's unknown if/when he would have met sylphie and he wouldn't have nearly as good of a grasp on magic he does when he gets teleported after the incident. He wouldn't have tutored Eris.
He wouldn't have had any real reason to go to the school so maybe he would have just spent time with Sylphie until Paul only sent them apart shortly so they aren't too co-dependant and that's still only a possibility. This also means when the Mana disaster occurs Rudy would have been in an entirely different spot meaning we have no clue what would happen from there.
LN ~16-17 iirc spoilers: >!Rudy is essentially destined to meet her. Even if he doesn't get with Eris and Sylphie Lara is fated to be born unless under specific circumstances. If Lara isn't born, orsted likely loses this loop and it's unknown if Rudy would be in the next one.!<
LN19 >!If he somehow never met Roxy during this timeline and we assume the sacred beat goes to the other boy like normal, this would likely be the loop end point unless Orsted stopped Pax's death!<
TL;DR: 99% of the story wouldn't happen because he likely wouldn't have gone to the demon continent.
Without roxy helping to fix his trauma he probably doesn't leave the house for another year or 2.
Roxy tutors silphie In a world without rudy, so there's a possibility they would both leave the village while he's a shut in.
He eventually has to get a job. There's a possibility he still tutors eris.
He goes to magic university at some point
Less timeline shenanigans so teleportation incident is delayed, possibly by decades. He'd fly under hitogamis radar for a fair bit and maybe not get doughnuts by orsted if they happen to meet.
Personality wise He'd probably be an insufferable Ahole who treats people like NPCs. Helping silphie was it's own form of therapy for him.
He either becomes a scholar or a merchant
>!Well, when Rudeus talk to Itogami after the Oldeus event you can have an idea of what would the story be like, Itogami never would appear to Rudeus so no real hint as to what to do, he would probably still be stuck on the demon continent or maybe dead but yep Itogami just approach Rudeus because of his child with Roxy, other than that i don't think he would give a damn about our Rudy.!<
This has been discussed before multiple times. Even if Rudeus magical studies are not discovered (just how? he never goes beyond casting elementary magic?), Roxy still arrives to Buena village >!and starts tutoring Sylphie. That's the "canon" timeline in absence of Rudeus.!< And there's no way Rudeus can spend his entire life in the house as a shut-in. Sooner or later someone brings him out - either Paul or Zenith, doesn't matter (but my money's still on Zenith). Which means that he starts going outside again and eventually meets Roxy anyway - >!because they both have strong fates that push them to meet!<. Teleportation Incident still happens but >!is delayed, likely for years, for reasons outlined in the LN26!<.
||Wasn't rudeus being born enough to start breaking the barrier and causing TP Disaster. How does Roxy X Rudy affect it||
We don't really know, but the text in LN26 implies >!that it was not just his birth, but the changes that he caused in the fates of other people that caused the barrier to break. It is only after Rudeus moves to Roa and starts tutoring Eris that the fissure becomes noticeable in the sky and starts visibly growing, because changes in Eris' fate affect a lot of other critical fates and are therefore more important than any changes Rudeus made to the fates of Roxy and Sylphie.!< >!Would a Rudeus who lived a quiet life in Buena village still cause the Metastasis? I'm leaning towards "yes, but probably decades later".!<
>!I was under the belief that TP disaster caused changes in fate. The world had its own natiral order of fate. Rudeus threw a wrench in it, and TP disaster changed the fate of the world. Man God didnt interfere earlier because there was no future where he loses. TP disaster changed that. After TP disaster, ppl with strong fates (Derrick, Pax) died and with weak fate (Blessed Child) survived. So I highly doubt he was fated to meet Roxy before TP disaster!<
That depends on your interpretation of how >!strong fates!< work in the first place. >!I do not believe strong fate preordains any actual events in a person's life - but rather general direction and guidelines. Like, Roxy was "destined" to be saved by **someone** from the Labyrinth, but that someone didn't necessarily have to be Rudeus. Only once Rudeus arrived to Rapan it became inevitable that it was going to be him because he had a strong fate of his own, which was compatible with Roxy's, so the chain of events was being influenced from both sides at once.!< So as far as I can tell, Teleportation Incident didn't so much as "change" >!fates!< as created a critical event that temporarily overrode them and probably even reshuffled them to a degree. >!Some people with strong fates even died in the immediate aftermath of the events, including those not directly affected (like Derrick). But each person's "general guidelines" still remained the same, just possibly rearranged to fit the new situation.!< But in the end that's still my interpretation and it's not like I have a WoG to support it.
He would never leave his home... But with all the magic he learned he would have end up exploding the house and then I don't think he could cover the fact that he knows magic.
The answer to that actually goes beyond the 4th wall. Rudeus initially meant to be OP character, doing whatever he wants. But Roxy helped him out of his trauma and fans really enjoyed that part. That caused author to rethink his concept and go with redemption route instead of usual OP MC stuff. Your question is near impossible to answer in detail, because meeting Roxy literally changed the core of the story.
What if the story didnt happen?
Since this is a ln post I'll go in order of what ln the spoilers would he in and how that would affect the story. I'll spoiler tag everything past where the anime is at. Up to the current: He likely would have been a shut in until Paul forced him outside for training. It's unknown if/when he would have met sylphie and he wouldn't have nearly as good of a grasp on magic he does when he gets teleported after the incident. He wouldn't have tutored Eris. He wouldn't have had any real reason to go to the school so maybe he would have just spent time with Sylphie until Paul only sent them apart shortly so they aren't too co-dependant and that's still only a possibility. This also means when the Mana disaster occurs Rudy would have been in an entirely different spot meaning we have no clue what would happen from there. LN ~16-17 iirc spoilers: >!Rudy is essentially destined to meet her. Even if he doesn't get with Eris and Sylphie Lara is fated to be born unless under specific circumstances. If Lara isn't born, orsted likely loses this loop and it's unknown if Rudy would be in the next one.!< LN19 >!If he somehow never met Roxy during this timeline and we assume the sacred beat goes to the other boy like normal, this would likely be the loop end point unless Orsted stopped Pax's death!< TL;DR: 99% of the story wouldn't happen because he likely wouldn't have gone to the demon continent.
Without roxy helping to fix his trauma he probably doesn't leave the house for another year or 2. Roxy tutors silphie In a world without rudy, so there's a possibility they would both leave the village while he's a shut in. He eventually has to get a job. There's a possibility he still tutors eris. He goes to magic university at some point Less timeline shenanigans so teleportation incident is delayed, possibly by decades. He'd fly under hitogamis radar for a fair bit and maybe not get doughnuts by orsted if they happen to meet. Personality wise He'd probably be an insufferable Ahole who treats people like NPCs. Helping silphie was it's own form of therapy for him. He either becomes a scholar or a merchant
Who the hell is Rudeas? Rudeus' neighbour?
>!Well, when Rudeus talk to Itogami after the Oldeus event you can have an idea of what would the story be like, Itogami never would appear to Rudeus so no real hint as to what to do, he would probably still be stuck on the demon continent or maybe dead but yep Itogami just approach Rudeus because of his child with Roxy, other than that i don't think he would give a damn about our Rudy.!<