I'm afraid I can't say much about Jin as far as his wikia page goes, I'm sure he has a very interesting background, but hey, even if this opponent seems far too strong, considering how popular his series is, I will still do my best to campaign with all I have! And hopefully, even if I lose, that you guys will remember that Prince of Tennis is not only home to the fujoshis! I hope we will have a nice debate!
Let's go to the vouching.
So, as those who may have read my previous thread have noticed, I like to emphasize that Saeki himself is just naturally, the best kind of husband you can have. He's loved by his peers, juniors, and elders because of his nice and unjudging demeanor, an all around ace when it comes to sports (despite losing his most important matches, but hey, he's not even a minor character :'c), and good at academics and participation alike. The guy really screams friendliness and fair play. And he's canonly handsome. So charming and handsome that the two confirmed straight dudes fell for him. Just letting you guys know.
Now you might think, isn't that kind of boring? The way you describe him makes it seem like he's just some shitty dating sim guy, dreamy and unreachable.
Yes and no. Saeki's charm is that he himself is blissfully unaware that he has these qualities. He genuinely doesn't know he's popular and loved, despite many saying otherwise, and while that can be irritating, it also helps us avert the personal "omg im so perfect i have to keep up this appearance and i have so much stress and anxiety waaa" personality that most ace archetypes have. And it's not that it's a bad trope or anything, but the way Saeki is handled is just different. He has no weird complexes. And he doesn't need to have them to be a likeable , interesting character, or at least not for me personally. It's a nice change to have someone who is nice and cheery without having to be worried that they're hiding a buttload of angst beneath that mask.
What you see is what you get, and he will always be true to his roots.
Does this mean he has no flaws? Oh, for sure he has them.
He's stubborn and holds grudges. Depending on how hard you wronged his friends (yeah he's a total bro and the only grudge he holds against someone is cause that someone kind of killed his sensei), he will go from being passive agressive to legit throwing knives. Not a nice husbando quality, but I mean, he does talk to you unlike....this samurai guy. And unless you're looking for a guy that loves you shitting on his friends or those dear to him, you won't encounter this side. He's a tad egotistical, behaves recklessly, which, while it may seem cool at the moment, is not the best course of actions to take in a future relationship. However, this guy is not yet an adult, but displays already great maturity, so I'm sure he will grow out of it.
As for Jin...Well as I said, I don't know anything about him but...his hair looks greasy. He seems to be considered handsome by his peers, but consider. This is the Edo era (1603-1868). The first good toothbrushes were invented in 1885. From animal bristles. In the USA. You can't even kiss your husband without being afraid of getting Japanese plague. If, and if he uses shampoo (which he should considering the namesake of the manga) it was probably Tsubaki oil. It's used to cover up the stench of not washing your hair and giving it a fake shine (think as if you dropped your head in coconut oil for the non baldies out here). Be safe and go for the modern guy here.
He also only seems to talk in grunts. Now this might be considered ample communication for dudes, but some girls beg to differ. Like me. Husbandos should not only let their actions talk for them, they should be able to communicate clearly. Are those high standards for me? Hm.
He killed his sensei (probably with a good reason). He kills by mentally reviewing his opponents. Do you want to date a psychologist? Cause the divorce rate for psychologists is 19,30%, which is well above the national average of 16,96% (USA). Not a good choice after all.
Agricultural engineers are at 1,78%. Now guess what Saeki's dad is and what Saeki will aspire to be...
Anyway, since this is a clear clash of "husbando that is chosen cause they're megafrikkin awesome" and "husbando that is chosen cause he is a husbando" (which is subjective anyway), this will prove to be an interesting battle. I hope even the ones who participate with the first definition in mind will see the charm and effort Saeki has put in! Have a nice day!
Since I didn't use images in my last campaign, have a Saeki!