obsessive and distractable
Depends on the chara! "By default"... no, not even really that; it's barely a fifty-fifty mix.
Kiseki and Yoru, as well as most of the non-main-character charas, certainly seem to be this. They're monomaniacally focused on their specific theme, and don't really act outside it. That might have been a lack of screentime, but Kiseki gets plenty and doesn't change much.
Eru's a weird case. She starts out that way, but gets so much negative feedback she starts pushing outside her role just to get some results. So that's
possible, but I imagine that most charas in her position would disappear instead. Utau still wanted Eru, despite thinking of her as useless... though admittedly that's mostly Iru. They've landed in a much better balanced situation, it's just that modern-day Eru acts relatively little like her 'role' would have her act.
Iru, it's hard to say. Her focus is 'rebellion', sometimes against herself; her lack of predictability is part of her base character. She's far, far nicer than she used to be. I'm projecting her line of development throughout the manga, and landing at "similar to Utau, except cheekier".
...
Nana -- Lulu's chara -- is a bit of a weird case. Scratch that; she's a completely upside-down case. Lulu
wants to be an elegant lady, with straight hair and refined language and- Nana is the exact opposite of all of those things. She is, explicitly, the side of Lulu that Lulu tries to suppress.
Her eyes are blue, which is a bit of a pity. Though she's just copying Lulu.
But besides being an unusually sane shadow-self, Nana is also Lulu's sounding block. Lulu knows, on some level, that Nana is a genuine part of herself. They're brought into the story well after they've grown used to each other, so we don't know how that relationship started, but I imagine there was some attempt at rejecting reality in there. Though Lulu, considering her family, wouldn't have gone through anything remotely like the common case.
Nana is a very noncentral example of a chara, and might not count as one at all. In the present day she also doesn't exist, however; Lulu accepted her, and as such she... 'disappeared' isn't right; Amu was talking to her on the phone the other day.
...
Ran, Miki and Su were very much people by the end of the story, and Miki already acted that way right from the start. In her case, that's again a response to negative feedback; Miki nearly died right out of the gate, being a side of Amu that... honestly? Amu doesn't really want. Still
is a side of her, but externalising it as a separate person seems fair, and probably healthier than making her a Shadow. Which might be where that would have otherwise gone, if the rest of the situation wasn't such a mess.
Amu spent more than one evening just quietly chatting with her sisters, while Su tried to learn sewing, Ran read manga next to Amu and Miki sketched the scene... that's on-screen. I don't think it's the default behaviour for charas, but it
is what Amu
wanted.
Miki didn't disappear, however. Because she informed Amu of the situation, and Amu -- being Amu -- determined to keep Miki around and... at least
try to be that sort of person. It worked well enough to fool the system, I suppose, even if Amu never actually wound up taking on any of Miki's character traits. That didn't work forever, but by the end of the story Amu was capable of going "nuh-uh, I'm keeping them", and having that stick.
(At what cost to herself?)
The same is true for Eru and Iru, really. For Utau it's more of a balancing game; she literally isn't capable of becoming both of them at once, but probably the natural outcome for a situation like that is still to have one or the other fade, then fuse with the second. She refuses; Utau likes to keep the two around, as something between familiars and friends.
...
There is no one-size-fits-all template for charas. We've seen everything from "might as well be a shadow" to the exact opposite. We've seen charas reflecting dreams that are
literally impossible, charas reflecting dreams their host had
essentially already achieved, and everything in between.
This should be expected. They're the product of a literally intelligent process, and no two minds are ever alike.
