@Huumin: isn't it on the contrary the right time to advance some of the plot? Like they're currently recruiting their main DPS basically, they just need to clear the situation on their relationship (since it's the reason Sauro is staying) or at least put it on hold for after they cured Vivian, and explain some things to him...
More precisely I've re-reading some chapters, and I'd really like to now see Arsenio and Sauro talk about a few stuff:
- I'd like for him to explain about the pervy cow (and clear the misunderstanding about Arsenio saying he was one of the demon king's underlings too) and Vivian. With Sauro helping with this, they finally have a hero lvl99 joining the party, but he needs equipment. I can see Betty asking the hedgehogs tailors to make him some solid magical clothes. They could also get him a shield - I find interesting that he called himself Arsenio's sword & shield after all, that could have been foreshadowing for him to yield and actual shield too and not just being a swordsman. And of course talking about that...
- I need Sauro to ask Arsenio about his dreaming of forging magical weapons, and if he could furfill his promise to make him a sword, one that would finally be solid enough to never bend or break (Excalibur/Caliburn, come one Mochi I'm counting on you). It might take some time, Arsenio need to re-train, and possibly rare items, and that could make some interesting scenes and adventures for a bit.
- finally, and this definitelly should happen soon now right, Arsenio needs to tell his story of how he met Betty and explain what exactly entails their relationship/contract (this might happen when Rei, Lloyd and Eric are around, as they might want to hear about this).
- and this is less important to the plot but, I'd like for Arsenio to ask about his parents - I don't know how the prequel ends so they might have died before he left Espania, but in the case they're still alive I kinda want to know what happened with them and see Arsenio's reaction.
In brief, I just think that in the contrary now that such a powerful character is with them, things can move again, maybe?
ps: I'm pretty sure NTR imply cheating like
@PanicTears said, so I'm not sure why anyone would call it that in the case of Rei x Arsenio either, it's not because one of the character confess to the other one that it means they're definitely together. He showed that he was happy they liked him, and he said maybe, if Rei kept a female body, and when they're older, but they're not actually together yet (the fact that for some people NTR is worse than to jump a minor though is... something haha)
Also honestly what's with this idea of being against an end game pairing just because one of the characters appeared later, as long as it's not some random person showing up at the very end I don't see the problem. Using one of the most well known manga out there again: most people have no problem with Bulma ending up with Vegeta, and he appeared v17! Their relationship, his chara development, and Trunks' story are some of the best things about Dragon Ball. Sometimes you just need to chill, and don't root hardcore for the first boring/awkward boy-meet-girl pairing, and give a chance to something more interesting even if it happens later... But for what it's worth, this being a shounen there is a chance that in the end they just stick to be a big and happy platonic found-family à-la-Gintama lol