
Observation: Most of the Majin Tantei Nougami Neuro manga is written in limited-third-person-Omniscient.
(Digression: Comics/manga are MUCH less tied to PoV than prose, and seem to mostly probably fall into some degree of 3rd-Omniscient; I've only really seen ... well, one thing I could honestly call mostly first-person and not even "close limited third". It's a now-oldish Dark Horse released Bubblegum Crisis offshoot, I have it somewhere but don't remember the exact title; it was narrated by, and a lot of it was quite likely "perspective of", an AI.)
I call Neuro mostly limited third because it's pretty damn obvious that, whenever there is narration outside of what's explicitly shown in panel, Yako's the one narrating. There's chunks that are obviously nowhere NEAR her sphere of awareness, but a lot of the major arcs have commentary and "narrator voice opening/ending/other box-text" that's Yako, and there's an implication that while it's not likely she knew the "fly on the wall saw the event" details of a lot of the scenes outside her sphere, that at some point, she gained a general idea of the situation that those scenes would relate to. (And let's face it, cut-aways like that are much more feasible to "convey information" than long blocks of narrator-monologuing like you'd get in prose.)
This makes the whole IC/OOC thing with Neuro throttle-worthy. It looks like all that we ever see of him is what Yako would know as of the nebulous point in time she's narrating from...
But the closest there is to honestly mentioning what's going on in his head, is his own comments and statements.
This gets more fun because... it's like trying to pull a serious psychological dissection of some of Shakespeare's more infamous unreliable narrators - does anyone honestly think Neuro is going to accurately or completely explain his reasoning and thought processes? Even when he does lapse more out of his cheerful dramatics to behave more seriously, he doesn't exactly go into depth, and the usual impression is that he's leaving a larger part of whatever is on his mind -out-...only saying what he'd need/want whoever's within earshot to know.
Comedically, getting Neuro IC is the opposite of what happened with getting Alessa IC before the movie and 0rigins. With Alessa, her background, history, and situation were all laid out, you had indirect views of her actions, but you didn't really directly interact with her much or see her directly interact much. (I had to cackle slightly when what I'd pieced out of her personality turned out fairly accurate to later canon, when she -does- get more of an "on-camera" part.) Neuro hams the camera... but just about anything background that'd be important is left out. Hell, there's the possible implication that the usual "Hellparrot" form that gets seen isn't even his full true form; when the manga has the brief cutaway to Neuro in the demon world, he's more human form than he even pulls later in the series. (Nevermind that the HAL arc is the furthest "hellparrot" he goes.) There is no mention of his past. There's implication that there's some kind of society in the demon world, but no mention of his role in it, or even any clear mention of what kind of society it is. It's implied that there's a distinct "alien psychology" situation going on, and a major culture-shock issue, and I've usually read it a step further - that the intent is to make it hard to assume -anything- about demon world society or get -any- impression of it having familiar qualities.
Oh, and I usually assume Neuro's own accounts of the demon world are another case of "unreliable narrator"; some of his stints of telling Yako stories about the demon world sound FAR too much like the traditional online-Alaskan game of "Let's fuck with the heads of the out-of-state people who wouldn't know better". If Alaskans can get away sometimes with conning people into believing that the entire state is a blasted arctic tundra, there are few cars, and most people get around via dogsled and have to daily dodge polar bears... ... Well, Yako doesn't even know as much about the demon world as the average Outsider would know about Alaska, so Neuro has carte blanche to screw with her head and make shit up - and screwing with her head is far, FAR too in-character for him for me to think he -DOESN'T- pull "Let's see if she notices I'm bullshitting" games.
In fact, his own explanations of his capabilities and limitations are probably not always reliable; he seems to make a habit of very rarely -LYING- so much as strategically leaving things out, but also very obviously plays games with keeping people off-balance in what they know and expect from him - so odds are, especially in matters where it could be life or death, he probably plays gambits of "I -have- limits, I'll admit I have limits, but I am not going to be open/'honest' about just where they are or when they're being approached". I've worked under the assumption that he plays that the way he plays the idiot act; he'll bring them up, telegraph them, act in manners that would cause people to think he was worse off than he actually is, for tactical advantage. (Ex., the HAL arc sphinx protected by gunmen.) He never actually codifies things like "How long it'd take for him to turn human", "How much abuse or power expenditure it takes to seriously injure him", etc., and with the contrast between his recovery time/behavior after getting whumped in the HAL arc and some of his later behavior, he probably hedges bets given the chance.
So as an RP character, he's someone where he has a very strongly established personality...but next to nothing in canon to explain the background processes of why he acts that way besides vague implications from his behavior and what he seems to expect or treat as "Normal". Yay flag!