Noel KreissThe last human of his timeline in 700AF, Etro (in true Etro style) took pity on Noel and opened the way to Valhalla, where he met Lightning. Lightning was the one that sent Noel, along with Mog, to Serah in 3AF.
Noel is Serahís partner in time. Wisely, Serah is reluctant to trust the mysterious young man right away, but they soon develop a close bond that lasts. Thereís a lot of reasons for this. For one, Noel was created specifically to counterpoint and complement Serahís strengths and weaknesses - being an unusual protagonist, Serah needed someone who would not outshine her or be overly forceful. She needed someone with similar priorities, someone who understands her wants and dreams; and she needed someone who understood what it was to be entirely alone. Someone who understood what it was to lose the person you love the most. Arguably, she needed a partner so removed from the original timeline to be a friend that was entirely hers, a friendship that the player would actually see develop on screen, instead of yet another inferred one, as is the case with most of the original party. Then, thereís Serahís semblance to Yeul, and Noelís semblance to Caius - they are the exact opposite of their adversaries, but fulfill the same roles. Noel becomes a Guardian to Serah, in an official capacity he never actually held with his Yeul.
Serahís journey would not have worked with anyone else in the cast, except for Noel - Noel highlights Serahís humanity, her smarts and her compassion, and she in turn highlights Noelís strengths. They are perfectly matched.
They also never argue or are at odds: it isnít needed. They have plenty to challenge their resolve elsewhere without testing their friendship, because their shared journey and its outcome is trial enough. The player sees a lot of Noelís fierce protectiveness of Serah, obvious and transparent, but itís not a one sided thing. Though she is at first reluctant, when Serah welcomes Noel into her inner circle, it is without reserve - she will fight and die for him, and will stand at his side no matter what. Heís family to her now - even if her heartís desire is being reunited with everyone in New Bodhum, she always feels thereís something missing if she accepts it, and thatís Noel.
Really, they both epitomise something that is so often not seen in many forms of media - two people who are life partners, of opposing gender, without a lick of romance. There is nothing between them, no crush or dalliance or flirtations, no matter what another characterís opinions are about them crossing time together - theirs is not a relationship about falling in love. Itís about utter and absolute trust between two people, of acting on shared thoughts and dreams.
Most of the time there would be a hint of romance in a relationship such as thisÖ but there isnít. This is something the world needs more of. We need to see more positive portrayals of two people (especially of opposing gender, Iím looking at you, mainstream heterosexual movies) who donít need romance in their story to build a relationship that endures and stands the test of time. Serah has Snow, Noel has Yeul, and thatís never in question. They talk about it, how Noel envies that Serah can be apart from Snow but not love him any less, to be so secure in their relationship that they can stand not being together all the time.
Serah will never be Noelís most important person, but sheís one of them. He isnít affected any less by her death - Serahís loss destroys Noel in a very final, damning way. Sheís not the first person heís lost, not the first person heís promised to protect and failed, but she was the person he stood with, tasted success with, and lost anyway. Together there was hope. Alone, he has none. Just like everyone else in Serahís life, he believed in her, and at the time, he is naive enough to hope she will survive. Coupled with the fact the emergence of Nova Chyrsalia meant Serah died for nothing, this is Noelís tipping point - the straw that broke the camelís back, as it were.
But never does he blame her for it.
And when Noel realises that the only thing that would make Lightning turn against Bhunivelze is Serah, he clears her a path to allow her to reach her goal, because he gets it. He has his own heartache, and he was there for Serahís wish of seeing her sister again - and though it might not be his duty to retrieve her, he was her Guardian once, and he sure as hell is going to make sure Lightning has the best chance possible in doing so.