Satoshi's Personality:
Satoshi falls initially into the stereotype of the cold and aloof teenager, because he's quiet and keeps an emotional distance from everyone. Smiles are rare for him, and genuine ones almost non-existent. Mostly a loner, he takes little interest in the activities and affairs o others and doesn't contribute much to group activities he doesn't have to, mostly going along with the majority opinion...and often tends to do things on his own even while pushing for others to cooperate efficiently. Almost always calm and collected, he can be pegged as one of the most mature people in any group and can be hard for even people he deals with regularly to read.
Extremely intelligent and observant for his age, he is good at planning and directing others helpfully. He normally takes the most preferable method of doing anything and makes note of things in case they need to be recounted later or so he can keep track of things...as such he always carries something he can use to take notes with. Very little seems to escape his notice, and his eye for detail borders on unnatural. Even in failure he learns from his mistakes and that pushes him even closer to success the next time. It irritates him noticeably when others work inefficiently during serious situations, though he won't waste much time telling them some once it's obvious they won't listen.
Beneath his cold and distant nature, he's actually in a lot of emotional distress. He tries to avoid attachments for fear he'll lose them, believing that everyone loses everything eventually, it's just a matter of how long it takes and therefore people only gain things to lose them...and he hasn't enough time left to waste on such things. Though he also feels that he'd be the one to destroy anything he became close to. This fear is so strong that should he suddenly find himself becoming attached his first instinct is to push whoever it is away or even try to escape the feelings.
Because of this insecurity, he doesn't dare feeling anything to strongly and so doesn't really understand strong connections that hold through apparent betrayals of a serious nature...though he can display a large amount of loyalty to those he cares about, going out of his way to help them even if they're supposed to be his enemy. The thought of hurting such a person terrifies him to know end, but once he comes to accepts that person as close to him there's a sort of relief and happiness from that despite the pain it causes him.
Among his noticeable character quirks, are his disregard for personal space and his tendency to almost appear RIGHT THERE with little to no notice. He moves unusually quiet by nature and it's just a given that he often startles or catches others by surprise because of it. He's not above physically impeding a person's progress when he needs to, especially if he needs to speak with them alone...which may lead anyone who is an outside observer to question the nature of what's happening. He's somewhat cryptic when he speaks at times, offering very little information or saying things that can be taken the wrong way without that being his intent.
Offsetting his highly organized mind and work habits, Satoshi's living area usually a disaster area, not dirty but very untidy. He can still navigate and find anything he needs with ease though. He shows little concern for his own health, seeing to his hygiene but rarely resting or eating more than the minimum he can manage to keep a pretense of normalcy.
Satoshi's Abilities/Additional Notes:
As a Hikari, Satoshi's most powerful abilities revolve around art, those these are only touched upon since he prefers not to use them. He can create and give life to artworks, making powerful and possibly dangerous beings with unique magical abilities. He can also destroy these kinds of artworks or restore them. He can seal or limit their powers as well given the necessary means to. And he possesses knowledge of every artwork the Hikari made, whether it was destroyed or not, and what they're supposed to be capable of...as well as sense when their lives are ending and "hear" them.
Also a a Hikari, though this ability doesn't appear to have anything more than his eye for detail, excellent memory, and family's inherent talent as the source...he has the ability to perfectly recreate any painting and probably drawing that he's seen before in a matter of minutes.
And finally as a Hikari, he shares a body with Krad, the white winged half of the artwork "Kokuyoku" as unwillingly as that is. While his transformations are initially caused by Daisuke, Krad has taken over to protect him as well...though this is because they both die if Satoshi does.Krad is a constant presence in his mind so he rarely has privacy and has moments where he apparently can't truly be sure which of them is in control. Having Krad shortens his life and puts him frequently in pain or makes him suffer tiredness that he keeps to himself and full transformations when he's conscious are usually bordering on agonizing. Sometimes he is able to fight Krad's control of his body and forcefully regain control.
He is highly perceptive, noticing things others wouldn't: from things like hidden cameras and trap triggers, to being able to a differences in a river's flow at a glance. Doing something near him carries a heavy risk of him seeing it even if done subtly...and him not being in the immediate area does not mean he's not somehow watching either. Though his physical abilities are pretty average, Satoshi does have a higher pain tolerance threshold than other people because pain is normal for him. As such he gives most injuries little to no mind and may fail to notice them at all if they're not major. He almost tends to push his body when things need to be done, pushing himself on sheer force of will...though he may eventually pass out from sheer exhaustion if he pushes his limits too far.
((General Note: In the anime it's stated that he can't create art of his own and in the manga he says something similar to Daisuke, though a flashback near the end shows him doing so at a younger age. This makes it much more likely that it's personal choice not to.))
Krad's Personality
Not a whole lot is known about Krad's personality. He's shown to be very proper and is usually as composed as Satoshi, always speaking politely to others. He's also intelligent and fairly cunning, but is murderous and despises humans, having no desire to be bound to the Hikari family or apparently to even exist in the physical world...though he does intend to gain full control of Satoshi's body and claim it as his own. He's also shown absolutely no compassion for anything or anyone ever. If he dislikes them or they're an obstacle, he has no qualms about crushing them.
While possessive of of his Tamer, calling him "my everything" and claiming to love him so much, as well addressing him as "Satoshi-sama" implying he is master, Krad does not listen to Satoshi and has no concern for his well-being. He always uses his full power regardless of the damage it does to Satoshi's body, and never interferes with interactions between him and his father...even when the man had him pinned to a desk and cut his hand with a knife.
He despises Dark, and does not hesitate to try and kill him at any opportunity, also mocking him whenever he can and taking great pleasure in causing him emotional turmoil and physical pain. He also hates Daisuke and does attempt to kill him as well, refusing to call him anything other than "Wing Master" or "the Niwa boy" when talking to or about him...though this is just as much because of Satoshi's attachment as it is who he is. He perceives Daisuke as a threat to his existence, believing he is corrupting Satoshi.
He has no compassion even for the other artworks and in the most recent chapter, he expressed that he would destroy every other artwork the Hikari created to see what he would become in the end. He doesn't care that destroying Dark will mean destroying his other half, or what happens to anyone else in the world as long as he has Satoshi.
Krad's Abilities
Krad has wings and great magical power because of what he is. He's able to erect barriers and use blasts of energy, use what could be considered a form of telekinesis, as well as attack with his feathers in various ways...but using any of that power puts an enormous strain on Satoshi's body and overuse could easily kill him. The wings actually leave two narrow wounds where they burst from his back.
He is able to force control of Satoshi's body when he feels the need to, though to an extent Satoshi can sometimes regain control. When not in control, he can appear as a sort of phantom version that only Satoshi can interact with or hear.
In recent chapters it was shown that Krad was likely the Hikari who created Kokuyoku, in which case he would also have the magic the Hikari use in their art.