Some trivia, some character exploration. Mostly random babbling.
-Light still thinks in Japanese, instinctively - for the most part, anyway. It's probably a bit of mix, 'cause I'd say he's fully fluent in English, but Japanese still comes just a few degrees ahead.
-He associates different personalities with each language. Which doesn't make much sense at first, maybe, but basically - in his mind, there kind of is an "American Light" and "Japanese Light". When he came to America, he became a very different person, and a lot of it was caused by the going-to-America; so there's a (largely subconscious, I believe) divide between the Light who is Japanese, who lived/was created in Japan, who speaks Japanese; and the Light who is American, who lived(s)/was created in America, who speaks English. There are entirely different personalities and self-images associated.
-I think the move to America was actually a really destabilizing, even traumatic? experience for Light. Because, given his personality and identity - well, he's a perfectionist, his self-image is that he excels at everything, he's prodigious and impresses people. And yet, when he came to America... well, Light's a genius, yes, we know this. But as far as I can tell, the time it takes for average Japanese speakers to become fully fluent in the language is 5-8 years. Light's above average, obviously, but the point I'm getting at is that... he was ten years old, he had no English or next to no English, and he was suddenly plunged into it. Super-intelligent or not, he wouldn't have picked up much more than the basics of the language for months. I have yet to concretely decide how long it took him to learn, but I think after a year he had good communicative and understanding skills. By two years he was fully caught up to his age level. By three years, he started to feel fully fluent, was speaking English at an above-average age level, and it also came truly naturally - thoughtlessly, as in, no hesitations to make sure he was saying it right, no having to run it through an internal translator - not so much Speaking English as just speaking.
Which nevertheless leaves us with a good, pretty long while (especially long for a ten-year-old) which must've been nightmarish, in which he couldn't communicate properly, couldn't understand properly, and basically took a huge fall. Suddenly, he wasn't a prodigy, wasn't able to impress people, wasn't excelling. He was probably confused, (felt like he was) failing, felt like he could only possibly make a huge fool of himself, felt like an idiot.
And. Yeah. Issues. It's the kind of ego-knock which Light never received in canon; accordingly (with that AND the family-rejection thing) I play bassy with more insecurities (and various other adjustments which follow logically) than I would, say, an OU!pre-canon!Light.
-Some more alterations due to culture and the family rejection. More the latter than the former, actually. Light swears; he's more informal and casual; it's not exactly part of a "teenage rebellion" - although, of course, it totally partially is. It is, however, also partially more permanent/stably considered; a reassessment of priorities and self-image.
-When he was a child, he made a detailed plan of his funeral, in the same way some people/girls plan out their weddings.
-He loathed - and still does, probably - the thought of anybody being in his room without him knowing.
-In the past two years, Light has, in fact, thought frequently about trying to patch things up with his family. In the end, though, he's both too proud and too vulnerable. He won't reach out to them if they won't reach out to him first. It would, he reasons(ed), be perfectly easy for them to track him down and call him; but, since they haven't, obviously they don't want to. Therefore, he's not going to exist in neediness, requesting their forgiveness and a renewed relationship
-Light has a general complex about not caring about people individually - he has this persistent, disturbing feeling that caring about individual people is horribly self-centered, and betrays just how small his existence is - if he cares about the fate and emotions and life of people he knows, he'll have to face that he can't care that way about all the billions of people in the world whom he hasn't met and never will - and, therefore, he is far smaller than he'd like.
So, throughout his life, Light has routinely pretended that the personal connection is the lie, and the intellectual concern for the fate of the world was the true emotion.
However, due to chance and circumstance, over time he has been forced to confront that he actually has come to care about people individually - that he can't keep on being so noble and fairly unempathetic after all. But he still tries to pretend that he is that way, when he can, because there's an impulse to still be that way - it was familiar, it was safe, it was a cornerstone of his identity. And it's shifting, and changing, over the past few years, and that frightens him; so he tries to gather who he used to be around him like a shield.
But Light has, as it were, betrayed himself to a fair number of people, so around them he can't really pretend to be that way. I think that's a reason that the personality-blurb I've got written up in his profile doesn't really match him very well, insofar as how he's actually played in the DR, and makes him seem a lot colder than he is. He still tries to present himself as being that person, instinctively, when he's forming new relationships; but at the DR, most of the relationships he has have broken through that, so he just doesn't bother.
Oh, god, this is all so incoherent. It will probably be edited, added to, whatever. Maybe eventually I'll process it and add it to that Official Guide to Bassy post-thing. *falls over*