Nex met Siegfried in the past when he was slightly younger, and being raised by Imyo.
Sharing a childhood past, the two were raised by the mercenary member Imyo in an unknown location far outside of the government's notice. While their childhood is kept mostly in the dark, its evident that somewhere down the line an event occurred where Nex was forced to leave for his own determined safety when the governments did eventually catch on to what Imyo was doing. Until that point, Nex and Siegfried were at first apprehensive toward one another and Nex seemed to disdain his very presence due to the grimoire's overshadowing effects of hatred. Many times Nex tried to get Siegfried to stay away from him, but he simply wouldn't listen to Nex and instead followed him wherever he chose to go just to make a point that he'd do as he pleased. As this continued, Nex began to push past his unrelenting disdain of his presence, and began to somewhat care for Siegfried, though he had a bad habit of treating him like a kid.
Nex one day had to leave without warning, unable to take Siegfried with him. This he knew would greatly afflict him but Nex had little choice in the matter at the time. Siegfried seemed to still hold it against Nex for leaving however but since then Nex hasn't seen him nor does he know him to be part of the government.
Having not seen each other in years their meeting in Episode 8 was less than pleasant. Upon learning that Siegfried had gone to the NOS, Nex came unglued and demanded a fight with him. Feeling that Siegfried betrayed both him and Imyo for what they protected him for, by joining their sworn enemy and who they were raised to go against. Siegfried's attitude ultimately, only proved to Nex that he hadn't changed much at all and absolutely refused to acknowledge his cause, disregarding him entirely and leaving their fight in quite a harsh manner. However, he holds a certain hidden remorse that comes out as anger later on where he swore he'd make him leave the NOS.
Nearing the end of the verse it becomes apparent that Nex did indeed care for Siegfried's well being a great deal, expressing resentment toward those who were behind his suffering for killing off Imyo and taking advantage of his clouded mind.
The two met again near the ending of V1, where the two both seemed to be here to fight Zaezel and Nex was dead set on not allowing the fight to take place still having a hidden concern that he would perish. Nex showed off this idea subtly by drawing attention in on himself, but Siegfried didn't buy it and antagonizes Zaezel continuously. Even during preparation to fight the two simply couldn't stop arguing with each other, Siegfried mirrored Nex's movement, each time the other letting off a remark. It became so bad that Nex wasn't able to deal with the sheer amount of arrogance Siegfried displayed to him, and instead shows that the two have reached a point of not being able to cooperate with one another as they break out into a fight with themselves rather than a mutual enemy.
It was revealed that much of their trust was broken when Nex left—Siegfried lost a lot of his will when both he left, and Imyo perished after. Even so, most of Nex's anger toward Siegfried was from the lack of concern he had with what Imyo taught them, and the idea that Siegfried had given up on everything throwing away his chances to fight their once mutual enemy—which Nex couldn't understand with how long he'd been enduring what he refers to as a "Hellish Existence", yet Nex keeps going not because he entirely wants to, but has to. Along with the idea that Siegfried had never once listened to him, including the times where Nex genuinely cared about his life and safety, while Siegfried couldn't care less was a key factor in the wedge. Siegfried's shift into childish arrogance, uncontrolled anger, and lack of concern with the world's situation made Nex disgusted to say the least—however after Siegfried utilized a powerful "Azure Void" and took both of them down with it, Nex decided to leave Siegfried to his own devices and gave up on trying to get him to leave the NOS. He instead put a blind faith in him to handle his own life, and wants to think that Siegfried knows what he's getting himself into.
However its clear that his instinctual protection over Siegfried hasn't exactly left him as he was willing to release the grimoire, (something he clearly said to Akuhei and Lukain he wouldn't ever do again) in order to gain the power to stop Zaezel from killing Siegfried.
Verse 2 Edit
Nex's first technical meeting he recalls with Akuhei is shortly after he'd been infused with the BlazBlue. Ever since that point in time, he grew a large hatred toward him. Akuhei had then been actively involved in many events which made his life difficult, even after Imyo had managed to get him out of the NOS's hold, Akuhei spent effort in continuing to have the SIA hunt them down when opportunity arose.
Now older, and seemingly no longer fearful of him, Nex uses his hatred of Akuhei to strengthen himself whenever he sees him and is quite quick to the draw to fight him if given the opportunity. The two despise each other in their own ways and have a deadly antagonism built into their very essence. Nex while having clear hatred of him, tends to keep a level head and avoid playing his games—that is until Akuhei gets into his head. Nex despises his ability to read into his every thought and emotions, though how he does it is a mystery to him. Nex has several reasons to despise Akuhei, but a key one is because of the fact he's in the SD Division (Sequence Destroyers) of the NOS. Nex is aware that Akuhei likely knows quite a bit, but he knows he wont talk unless its on his own terms. That noted, Nex being the destructive force he is, can't stand Akuhei comparing the two as similar in nature.
The two show an immense hatred towards one another, Nex proves to have difficulty simply ignoring him in his first encounter and gets into a problematic situation. The twos history appears to go back even further then when Nex first incurred the "Incident" as evident by his memory in episode 7. What exactly happened hasn't been said, but it can be assumed to have been at least part of why he hates him. Despite being told by Legna to avoid Akuhei Nex spent much of his time in V1 looking for him, especially after realizing that Akuhei had been involved in Siegfried's current situation. This only increased further upon hearing that he had sent Siegfried into the city to fight Zaezel according to Serza as he believed Akuhei sent him there to die—though he never was able to track him down.
Nex meets Myri early on in the first season of Control Sequence. He finds her and keeps her from joining the NOS removing her from the only life she'd ever known. Nex mentions that in order for his own road to succeed he can't let her join them, and that seems to be the only cause behind his actions. He tends to find her incredibly annoying and can't stand the rants she drones on about when she wants to go back home. The two tend to argue a lot and disagree in everything done, but perhaps the thing he can't stand most is that she constantly inserts herself into his affairs, or even his fights. For that he's said specifically to stay out of the way when he's fighting.
Meeting the White Demon in an unknown case so far, the two refuse to mess with each other or step in each other's way. Both of them have mutual contempt toward the governmental systems making them something of allies. Surprisingly Nex is somewhat tolerant of him and the two tend to get into several arguments jokingly, often surrounding each other's actions and coming off as antagonistic friends.
There is a matter of which Nex has issues with concerning Sylar, as Sylar is far more aggressive and power happy then he is. He doesn't have issues with causing ruin, in fact he sees it as an odd thrill, while Nex tends to avoid drawing attention or causing unnecessary destruction. But, in stark contrast, Sylar is more forgiving then Nex and willing to work with others. Even so, Nex is supportive of his cause.
Nex first met Fasado in Episode 9 of Control Sequence. He's capable of getting Nex hot under the collar, and making him tense in mere presence. Nex can't stand his dialect of interest towards him, and prefers to keep away from him if he can—feeling a certain unease around him. Having connections to both Akuhei and Lukain only serves to increase his dislike of the man. A matter he absolutely can't stand is the fact he refers to him as a "Lab rat". Oddly though Nex has felt like he was familiar but nothing has come out of the thought so far in the series.
A man who Nex despises for his own reasons, having a malignant feeling towards him. Later into Control Sequence in episode 16, Nex approached Lukain for answers about a few past events, and upon learning that he was in fact behind several orders as he'd expected. Said orders of the government hunting him after he'd received the grimoire, as well as the death of Imyo and by default then part of Siegfried's trauma, and Nex's resentment only grew. He desires to give him a fate worse than death, and see him suffer along with Akuhei.
Nex and Byakai meet each other once again in the ending of episode 6 and officially in episode 7. The two apparently had known each other in an encounter outside of Kagusutchi involving one of the Sequence Destroyers. Nex apparently saved Byakai from death by intervening in their battle, though not much else is known besides that and Nex doesn't seem to like talking on the matter much. Byakai is one of the few that Nex doesn't become annoyed with, and now that he's left LSZ the two can be viewed as allies to a degree.
Encountering him within the 2nd Arc of Rebellion Sequence, Heilo made a certain bond with Nex after saving him and proving he wasn't out to use him in his own agendas, being one of the few to earn the young teenager's trust. While Heilo and Imyo were both Nex's guardians, in comparison to Imyo, Heilo is stern, and mysterious as a protector and would speak of Nex about needing power and following his road he shied from, but always valued Nex's free will to decide his own fate.
Nex wishes to know more about him and the girl he protects: Xendes.
Xendes is a young girl who Heilo protects, she seems to have a fondness for Nex. Feeling he could relate to her, Nex seems to enjoy her company in the 2nd Arc of Rebellion Sequence.
Nex meets Abel in the 5th Arc of Rebellion Sequence. Nex doesn't seem to care much for his antics or dialect, as it tends to annoy him. Other then this though he seems to push him off as an eccentric zealot due to his fascination with the Goddess and the Azure-- but respects how he makes an effort to help others in Kanayama rekindle hope. He however, becomes very uncomfortable when he's called a 'savior' by him.
Ange is Komyo's current guardian and one who Nex meets in Kanayama. She has a gentle care for the man for some reason, and shows the effort to warn him of any dangers. Nex is seen to be extraordinarily calm around her.
Little is known, Nex develops a character relationship with Cetan and it's explored during the conflict within Ibukido in the storyline of the 6th Arc of Rebellion Sequence.