Konohagakure no Sato
Shinko Omawarisan - @SynAlthough Sakana originally reserved his opinion on the (late) hokage, the new revelations regarding his twin brother has made him wary of the hokage. Although he realizes that the hokage was a good leader, a lot of trust was lost the day the revelation was unraveled, and as a result, he is unsure where he currently stands on him. He has yet to be swayed one way or another. Loyalty to Konohagakure is one thing, but loyalty to a hokage is another.
Shizuka Ichimi - @SynNews spread quickly to Sakana that the team he'd found in the forest of death, namely Kurin Senju and Jaakuna Hiroko, had been abandoned by Shizuka Ichimi and his (now) girlfriend, Kiku Kurama. Sakana has no hard feelings towards him for now, but finds it hard to accept that someone who willingly abandons their fate like Shizuka would become a jonin. He has yet to see what the boy is capable of however, and if Shizuka changes his ways, might be more willing to accept him as his peer and equal.
Kurin Senju - @ReflectionSakana finds Kurin to be something of a worthy adversary, but has yet to see just what he can do. From their time in the academy, Sakana seems relatively disinterested in the boy, but is this really so strange? Now, after the events that unfurled in the Forest of Death, he seems slightly more interested, since Kurin accepted his fate and selflessly gave away his scroll to fulfill his desires - even if that meant death or not passing the exam. This is the same thing Sakana did, for different motives. Fate is interesting that way. Never the less, his kekkei genkai means Sakana is left with a strange, foul taste in his mouth. He'd have loved to burn this boy's wood to a crisp, but alas, fate did not seem to have span out to force them into a fight.
Usagi Orihara - @ProjectFrom their time spent together, Sakana has found that Usagi is perhaps closest to him in terms of personality, but furthest in terms of ideals and goals. A strange juxtaposition. Her actions during the exams have done little to solidify his trust in her, but he believes she cannot be blamed for what she did.
Hime Yuki - @GlitchybuggerAlthough not having seen her in action, Sakana remembers her mostly because she was one of the older participants in the exams (or perhaps he is one of the younger participants?). Despite not having a clearcut opinion on her, her kekkei genkai is enough reason to dislike her. And although he would know better than to go out of his way to tell her so, if she were to ever speak to him, she would be sure to be met with a wall of hostility and disinterest.
Kamui Uzumaki - @SpannerTheir slightly similar ways of talking and acting have been a good reason to bind the two of them together - both of them seem disinterested, although for different reasons. Kamui's willingness to help and aid Sakana is more than enough reason to rely on the boy, and his skill in fuinjutsu is a good reason to keep him around as a friend, since Sakana frequently uses the skill of the Uzumaki clan to get new seals on his body (and old ones renewed). Getting a discount for these services is always a nice thing. Alternatively, Kamui's skill in supportive roles is exceptional and expertly geared towards Sakana's fighting style, who is versatile and a jack of all trades - close range or ninjutsu, Kamui can be sure to guide Sakana in the right direction. And for that, he has earned Sakana's respect.
Nousagi Hyuuga - @ReflectionOut of all the clans, the Hyuga may just be the arrogant, 'enslaving' even those with kekkei genkai to be their servants. Although Sakana is well aware that their natural gift, their genetical... advantages give them the edge over him, he is sure to treat them with the same amount of disdain as other kekkei genkai users, if not more. Nousagi, being the heir, is not an exception to that, but more so the rule. The two of them are certainly not friends, though the question really is whether or not Nousagi even knows of the black-eyed fishboys' existence.
Kiku Kurama - @LadyinInkSimilar to Shizuka, Sakana does not exactly hold her in high esteem. Her fleeing from the scene of battle was a sign that she is not to be trusted in a real combat system and shows that Sakana could not rely on her. This, too, is fate. It is her fate. For him to get a better view of her, she must adapt, but the question is - can she, does she want to? Sakana does not bother to ask her these things, because he is disinterested in the answer. To him, she is more so 'Shizuka's girlfriend' than a person of her own.
Tsukiko Umene - @J8cobA worthy rival, although their styles are so different that they might as well just be regular allies instead of rivals. Their personalities are similar, showing a true pragmatic approach. Hunt - or be hunted. The choice is yours, and both of them seem to prefer to hunt. Sakana lacks her desire to go out and do it all by himself. This can be a pro and a con. Her attempt at betraying them, however, is much less a thing that he appreciated, although he understood it perfectly. His attempt to keep things together seems to have played into that quite well - a sort of mutual understanding between the two of them perhaps.
Iwagakure no Sato
Kyoka Haizenberuku - @PirouetteAlthough Sakana has a distaste for her kekkei genkai, he has to admire her capacities as a shinobi. He still think her kekkei genkai makes her a freak of nature, someone to put down, but as a shinobi he has to admit she is capable enough. He has not, however, seen enough of her to make a judgement beyond that.
Rumia Shinrikyo - @SavatoContrary to Kyoka, Rumia has shown more than enough of herself to make a judgement. Where Kyoka and others are purely a freak of nature genetically, Rumia is a true freak of nature, a freakshow that walks and talks. She is very strong - potentially stronger than your average shinobi from the Hyuga clan - which only drives Sakana harder to improve himself. He wants to be able to take her on, but that dream seems far ahead and far away as of yet.
Amegakure no Sato
N/A -N/A
Yomigaeri
Sangetsu Hozuki - @SeraphicideSano is possibly the first enemy that Sakana feels is much beyond his scope - even with team Fire at his side, he felt he would've been inadequately prepared to fight him. And he doesn't seem to be willing to tempt fate - he will fight Sano if they cross paths again, but he's not exactly going to go out of his way to fight the shark.