Kaito was one of the first two VOCALOIDs, created alongside his sister Meiko. With Kaito, the intention was to make him a teenaged male idol, so his personality was geared towards this. Not as advanced as the second series of Vocaloids that came later, however, Kaito's emotions were more the result of programming and were less fleshed out and human-like. In short, he was programmed to act like the stereotypical image of the teen pop star, and given an idealistic, simple, fun-loving, and romantic view of the world. What's more, his vocal technology was primitive in comparison to the later models, and more robotic sounding.
Kaito and his sister Meiko enjoyed some modest success, but the Vocaloid series didn't hit its stride and become super popular until the development of Miku, and the other Vocaloids that followed, Rin, Len, Luka, and Gakupo. When Miku was developed, Kaito was selected to help instruct her in the ways of the world due to his programming making it easy for young women to relate to him. And so, he instructed Miku in her development and in learning about the world, growing closer to her. Eventually, this blossomed into full fledged affection, with Kaito coming to fall in love with Miku. However, he was also painfully shy, and began to leave her secret admirer notes and gifts... with Miku's simplistic nature keeping her from realizing who it was.
His relationship with the other Vocaloids wasn't as... rosy. From the beginning, Meiko and Kaito had an antagonistic relationship, with Kaito being the more passive one. He also suffered a fair bit of playful abuse from Rin and Len, who would tease him like schoolyard bullies. Nevertheless, Kaito's bright demeanor and simple personality persevered, and he took in stride. He loved all of his siblings, and rarely got angry, due to his programming being so fully ingrained into him. Eventually, they were also joined by several "imitation" Vocaloids, who were accepted and welcomed into the family.
As the Vocaloids grew more and more poular, Kaito took a backseat role, as his younger siblings were much more famous than he was. He attempted song writing, but many people found his work to be overly saccharine. Nevertheless, he persevered, partly due to Miku's encouragement.
Then came the point where Miku, Rin, Len, and Haku all disappeared in a short time frame. Kaito was distraught with worry, and became somewhat depressed over Miku's absence. Gakupo eventually disappeared, and eventually returned, but Kaito could not believe the story that he gave to them.
Eventually, however, Kaito would find himself pulled into that same world.
⌈PERSONALITY⌋
Kaito was literally made to be a pop star, so he believes in romanticized notions of life and friendship that makes him, in some ways, seem like a shoujo manga character brought to life. He is also somewhat naive and simple minded, which makes him somewhat manipulable when it comes to his siblings. He possesses a great love of ice cream, of all things, and as he is a robot, he can afford to eat it all the time without consequence. Kaito is also a dedicated big brother, and remains supportive of his siblings, even if they run him through the wringer now and again.
There's also a part of him that knows he's not quite as human as the others, and it weighs on his mind, as he wonders if his affection for his family and Miku is real, or just part of what he was "made" to do. This insecurity makes him less bold in his actions, and he prefers to quietly support his family and friends rather than take action. This is why he has yet to act on any of his feelings for Miku, and partly why his musical career was scaled back. He also opens up more to girls than he does boys, in accordance with his programming.
⌈PARTNER⌋
YukiAgumon is exuberant and bombastic, and more than a bit hyperactive. He's also a stand up comedian. The problem is? He's not funny at all. After trying and failing to become a celebrity in Meria, he moved to Neon City and attempted to do so there. There... he met with pretty much the same success. Thus, while he puts up a happy front, there's a bunch of deeply buried resentment in him hidden underneath all of that bouncy loudness. He has a very deficient brain to mouth filter as well, and is prone to saying things that are thoughtless. Basically, he's a mixture of Robin Williams and Gilbert Gottfried, sans the talent.
