"I cannot see Guardshipping as anything more than a platonic relationship."
This was another one of those pairings that I did not recognize by name, so I had to hunt around a little before I could formulate an actual opinion on it. For some reason, Isono has never managed to make it into my headcanons on a regular basis, so that was a bit of setback. But, ever since I received this Ask, I have been slowly tinkering with it to figure it out better.
The way I see it, Isono has worked for Kaiba Corp. for a while. I could be wrong, and if there is evidence to contradict me from the series, I apologize, but I imagine Isono has been working there since even before Seto was brought in. And, if that is the case, I really doubt Isono would have tried to start anything with Seto, who was just a boy at the time. Isono does not strike me as the type to lust after children: if he was, he probably would have chosen a profession that enabled him to be around them on a regular basis, instead of working for the unmarried, heir-less Gozaburo.
Or, lets say that Isono did not start working there until after Seto had taken control of the company. Even if that were the case, no one in their right mind would try to either start a relationship with or get into Seto’s pants at that point in time. Seto was psychotic, as I believe I mentioned in my Prideshipping Musing. Unless you honestly had a death wish, trying to get close to Seto during that time would be a very, very bad idea.
I am going to work with the idea that Isono has worked for Kaiba Corp. since Seto was still a child, still ‘in training.’ I feel like, if he started working there while Seto was a tad insane, his ‘brand of loyalty’ towards Seto would be different than it is now.
It is not publicly known how Gozaburo treated Seto behind closed doors. However, given that the Kaiba’s mansion is clearly full of maids and other staff along those lines, I imagine that many people know at least hints of what Seto went through. They were ‘second class’, especially in that house, so I doubt many people paid them any mind as they went about their duties. That would have allowed them to see and overhear things that were supposed to remain secret. I doubt they did it intentionally, but once they had learned something they were not supposed to, I imagine they kept their mouths shut—they valued their jobs, and their lives.
Isono would be no different. I am sure he saw what was happening to Seto under Gozaburo’s care. But who really wants to stand up to a man like Gozaburo and tell him that he is raising his heir wrong? That was not Isono’s place. As much as it may have hurt him, or as often as he felt guilt over it later, it is likely he simply turned the other way and ignored it.
In my gradually developing headcanon about this relationship, Isono did whatever he could to help, without being detected by Gozaburo. If the man was in a foul mood, Isono would get permission to take Mokuba to the park, knowing of Seto’s deep desire to keep the littler boy safe. Things like that. He would help, without intervening.
And so, as Seto took over the company and developed into the young man we see throughout a lot of the series, I still think that Isono would not approach him as anything more than the majordomo-type worker he is. After seeing Seto grow up, even over those short years (there’s no denying that he grew up far more and faster than he should have had to), I think that Isono will still be able to see that little boy he had been when he was first brought there. To me, it seems very unlikely that Isono would develop any romantic or sexual feelings towards Seto in a situation like that. If anything, his feelings might border on paternal.
I have seen a handful of fans portray this relationship as having sexual qualities, without any real emotion behind it—Seto using Isono for sex in the earlier parts of his career as CEO. I can see where they are coming from with that idea, but I personally cannot work it into my own imaginings of this relationship. I am sure that Seto is more than capable of taking care of himself, should the need for sex arise, but frankly, I believe he had enough to keep busy with during that time frame to even really care.
And, from Seto’s side of the relationship, I highly doubt that he would develop any feelings for Isono. The man has been there as a worker in his house, and nothing more, there to tidy his papers when he is in a hurry and care for Mokuba when he himself is too busy to do so. He may not even realize exactly how much Isono has done and is doing for him as time goes on.
In short, I guess I just cannot picture this relationship breaching the line towards romance or even just sex. In my mind, Isono does care for Seto, in a way, but more as a protector. Perhaps he cares more for Seto than a worker should. But it is more born of concern for him than anything else.