yonamine kou
One
of the more enigmatic characters in Dragonaut, Yonamine Kou is
primarily portrayed as mix between an investigator and an ISDA researcher (though he describes himself as simply "an ally of justice"). He spends
most of his time following different characters (Jin, Raina, Garnet) and
trying to connect the dots between the various agencies in the series (ISDA,
Gillard, etc). He has an incredibly carefree approach to life, smokes heavily
and appears to embody the typical slacker-investigator type. Only not. Yonamine is actually from the office of the UN inspector general for space development monitoring. He first started observing the ISDA two years before the beginning
of the series and the UN considers him to be an undercover agent.
Yonamine keeps an eye on everything the ISDA does and files various reports to his superiors after the conclusion of each episode (these reports are available on the official website). After the time skip, it is suggested that he quits his position with the UN once he ceases sending in reports to dragonaut.com (subsequent to the events of episode twenty) and drops his UN pin on the ground (episode twenty-four).
Although he is involved in undercover work, Yonamine states several times on dragonaut.com that he isn't at all suited to fighting (information gathering is more his style) and as such, tends to avoid confrontation. His ever-present dog tags and handiness with a gun however, imply a history with the military. Several characters comment on how darn mysterious Yonamine is, but fittingly, we never seem to learn much about him.
with kitajima yuuri
We
aren't told how or when Kitajima and Yonamine first met, but it is clear that
they began a romantic relationship five years before the beginning of the series (episode
eleven). As Yonamine didn't start his undercover investigation into the ISDA until
three years later, there is no real context given to their affair. During
the majority of Dragonaut they are not together
(and why their previous relationship ended is never established), but Yonamine undoubtedly still
holds a torch for his ex. Kitajima on the other hand, tolerates her former lover only when he has something to offer her.
From episode one Yonamine consistently shares information with Kitajima he feels she might deem valuable even though he is not obliged to do so (he implies that she holds preference to any agency, that he "shows her first"). He also informs her of his movements when he leaves the ISDA base to gather information. During their meetings he flirts with her frequently and at one point, openly kisses her in ISDA headquarters (after which she punches him - hard). This affection appears to be fairly one-sided as Kitajima treats Yonamine coldly and is forever ignoring even the most genuine of his advances.
Yonamine's interest in his ex doesn't appear to waver at all, even after she escapes the ISDA and begins residing in Akihabara with Nozaki. Rather surprisingly, Yonamine is quite accepting of Nozaki's role in Kitajima's life and the three of them support each other a great deal during the last arc of the series. In episode twenty-one, when faced with a potentially life-threatening battle, Nozaki asks Yonamine to "take good care of her" (in an obvious reference to Kitajima). Yonamine says he will, but asks the Professor not to die in exchange. After Nozaki leaves in episode twenty-five, Yonamine openly laments that the Professor is being underhanded in sacrificing himself, as there's no way things will "work out for the best" now. Even knowing this, Yonamine continues to support Kitajima through the final episode. He stands with her, protects her from attacking Ostrums, and is by her side when she senses Nozaki's death.
For all her fighting against Yonamine's love, how Kitajima truly feels about her ex is certainly debatable. As a whole, she speaks little of emotions and does seem fairly ignorant of her own sentiments regarding others. She doesn't realise the importance of her closest relationships until something comes along and changes the equilibrium (as seen with both Nozaki and Nanami). There is no doubt that she still cares a great deal about Yonamine, appreciates his support and worries about his well-being, however, the series doesn't explicitly establish whether this translates into a continued romantic interest.
Through his contact with Kitajima, Yonamine becomes quite actively involved in assisting the Dragonauts and supporting the idea of dragon-human co-existence. Initially he is nothing more than an observer, taking pictures and noting the movements of others - never actively participating in any action that would support one side of the war over the other. His initial Dragonaut.com reports reflect the idea of an impartial observor in his clinical reporting of dates and events. By the time-skip however, it becomes clear that Yonamine is actually developing an interest in the world Nozaki believes is possible. He even goes so far as to steal and equip the submarine used to infiltrate Tartarus (at considerable risk to his own safety) because it's "what he can do" to support the Dragonauts. Yonamine's shift from impartial observer to active participant is an interesting move and one which relates directly to Kitajima's impact on him (in addition to the time he spends with the Dragonauts). As his ex and her dragon, so does Yonamine. The more time he spends observing and talking with them, the more interested he becomes in their cause. By the time Gio attacks in Thanatos's stead, Yonamine is prepared to die shielding the dragon eggs.
At the conclusion of the series, Kitajima and Yonamine together bear witness to humanity's restoration through the sacrifice of dragons. How being given a second chance by Nozaki impacts on them is not explored. Given Yonamine's actions over the course of the series, there is little doubt that he intends to follow Nozaki's instructions and will continue to protect Kitajima, no matter what path she decides to take.