Because it's impossible to play him without some.
**** - Stuff after something like that is something that made news, which others from his world might know about. There might end up being a handful of these for higher-profile cases as I get Saguru rambling about them. This would be something that's canon and known.
His parents are both very work-focused eccentrics, and police or investigative work of some kind runs in the family on both sides several generations back. His father's family has been Tokyo-era for freaking ever and is actually a fairly old family; the large western-style house they have in Tokyo now is more recent, and the older family home had been burned down in an arson attack a little after turn of the century. On his mother's side, there's also a family home in London, although it's half-inhabited most of the time.
(The pocketwatch is a family heirloom going back to the 1800's. The last time it stopped was in his great-grandfather's possession, seventy-four years ago, and thanks to his grandfather's notes, he can time how long ago that was to the hour. His great grandfather had broken his leg while investigating the catacombs under Paris and ended up trapped until he was found and rescued.)
Saguru's father is the Chief Inspector of the Tokyo Police. His mother is a professional semi-freelance consultant, who works for various law enforcement agencies including Interpol and quite a few local departments in various cities; her specialties are abnormal psych and behavioral studies, but she'd picked up enough of a scattered mush of disciplines to pick up on a bit more than her chosen field. She's based out of London but travels internationally. She'd settled in Tokyo for a while when he was born, and originally had every intention of staying there until he'd reached some kind of reasonable age, unfortunately, Saguru was ... Saguru.
A few things to note that are running things about his childhood:
1) His parents are distant. It's not technically that they don't care about him, per se, as that they're both very married to their jobs and not exactly people that possess half a clue what to do with a family or a child. For his entire life he's seen very little of them.
2) When his parents aren't there, he'd usually end up one of two places - either home with Baaya, who's been attached to his mother's family forever and is older than dirt, or ... at whatever police station was there, because it was really the safest and most reasonable place to leave him, particularly considering how he gets along with his peers. (When he wasn't getting into cases, he really was a fairly quiet kid that would be perfectly happy left alone with a stack of books and food.)
3) He does NOT get along with kids his own age. For one, he's a quiet, eccentric bookworm that was reading mystery novels, casefiles, and police procedure manuals when everyone else was on normal kid's books; he has basically nothing in common with them, and you know what kids are like to the quiet weird bookworm kid that makes no sense. For two, in Japan he stuck out as visibly foreign, and you know how kids ANYWHERE are with The One That Really Sticks Out, especially if they're also a weird geek...and when travelling he was always The Weird New Kid, and he did NOT have the temperament to deal with that by playing along or hiding out, so he actually tended to end up in quite a few fights when he was younger - which meant it was generally safer to ...NOT ... expect him to go spend time around other kids.
At any rate, he ended up hanging around the police station. Being that he was already a little Holmes-obsessed mystery freak that was overly bright, he tended to end up overhearing things and occasionally trying to help!
This is probably why the Tokyo police had any inclination to humor Conan. Saguru'd already broken them about "small children at crime scenes".
And while he WAS still a small kid, and not as good at putting the pieces together, he was very observant, and had already learned the importance of catching details people ignore, which meant that he tended to find things that DID turn out to be useful, and WAS capable of putting the pieces together, even if there'd be chunks of things he wouldn't know about yet or wouldn't quite grasp at that age. He turned out to be USEFUL, which surprised the cops, but got them to relax a little about having him around constantly.
This changed when he was seven and ended up picking out a few details and little things missed that pointed to a recurring robber they'd never been able to pin down getting away with it because one of the cops was on the take.
He'd managed to collect a bunch of little bits of evidence on the sly and quietly pass it to one of the older cops that was a good enough friend of his father's to read as "trusted", such that they were well on their way to actually making an arrest - except that he was brilliant enough to see the crooked cop going out suspiciously, and decided to follow.
The problem with being a blonde kid in Japan is that you STICK OUT if people have any reason to recognize you. Like say, "..isn't that the chief inspector's son?"
And he was quiet... but not quite as stealthy as he thought he was.
He ended up getting caught and held hostage by the robber, who was proposing to trade him for the evidence.
The rest of the police managed to catch up before that turned ugly, but it still highlighted a few very large problems; the kid WASN'T going to stay put, he -was- useful, but he was also very distinctive and a giant flashing target sign, because of whose kid he was.
This was when it was decided that his mother would take him and go back to London, and traveling like normal for her; in Europe, he not only wouldn't be as distinctive, but it's far less dangerous being "The son of that analyst who doesn't show up on criminal radar much" than being "the son of the Chief Inspector".
"Always the new kid"/"outsider" pretty well cemented that he usually stayed around the police stations, and ended up... basically raised equally by Baaya and various police departments, mostly Scotland Yard. He ended up traveling around Europe and being in and out of London with his mother for nine years. During the first couple years he was with the Yard, he started getting jokes about being "their mascot", and managed to be pretty well accepted there; as he grew up, he ended up being familiar to random police departments across half of Europe. He has a good list of case-experience between some of what he helped on in Japan and this, even though it was basically "helping" more than anything - playing assistant and doing what he could to get words in edgewise and get people listening to him.
{CARDIFF}
His first case that was "his" was when he was thirteen and working out of London; his mother'd been overly busy as usual, and had decided to see how he handled himself if handed one of the less messy seeming cases that'd been forwarded to her. It was a missing-persons case, a college student who was a little known for raising Hell and disappearing for a week or two at a time who'd disappeared and was gone a little longer than usual.
The problem was that Saguru already had Detective Luck. He may not be as bad as Shinichi, but he does have a bit of a talent for blundering into dead bodies; the problem is that while "Cardiff" was a very out of the blue thing, he's just as likely to end up with cases with multiple dead bodies ANYWAY.
It turned out there was a very odd sort of serial killer at work - one who was quite happily seeing how long he could work without anyone even realizing he was there, and who had been pretty careful to pick up people whose disappearances wouldn't be noticed; even had worked out an old chamber under an old church so that there wouldn't be any problems with remains being found and all that, and plenty of time to be had - none of the victims died fast, and he did have a fascination for some of the medieval equipment and torture methods. It was a bit of a fluke that a couple of the broke students he'd picked up DID get people looking for them, but there was so little evidence or clue that he wasn't exactly worried, until this stupid thirteen year old kid actually went and started spending time getting along with people that normally wouldn't talk to cops much and managed to get a few very wobbly leads - not enough to confidently mention anything to the cops, but enough to be on a trail to GET evidence.
So he tried to make the stupid thirteen year old kid disappear - the kid was by himself and didn't seem to have anyone keeping track of him...
Saguru actually has several nasty scars from this one, but did manage to get away, and use the church-bells to draw attention; he'd been missing for a few days, and there was a relative of one of the missing students that he'd mentioned the church to, so he got rescued, along with a couple other victims that weren't dead yet, and the killer ended up caught out of it while trying to get him down out of the bell tower, where he'd crammed himself up in the rafters.
****- There were three critical-condition survivor cases, he added another case of "injured", and thanks to the way remains were being stored, the numbers were a little hazy but slightly scary - thirty-six known dead, likely a good handful more. He ended up being known as the one who'd found the killer and led police to the killer's lair; news reports being news reports, he has a slightly heroic reputation from it that doesn't always mention that, as he'll put it, "I sort-of found that one with my face" - the killer found him before he'd caught the killer.
The infamous hat and coat were a gift, from the family of one of the students that had survived; they'd been intentionally, at the time, sized for him to grow into. He ended up with an odd sort of relationship there; not only is there massive sentimental value attached on a personal level, but it's VERY DISTINCTIVE and very directly related to a fairly large accomplishment. Part of the reason he's prone to wearing it on police investigations is just that reason - sure, he looks like a loon, but it also makes him very identifiable and points at his record, which ironically made it easier for him to get listened to by law enforcement in spite of his age.
{THAT ONE CASE WITH THE KIDS}
There'd been a series of disappearances of children around the age of eight or so; after a few incidents, a pattern was appearing - the kids would disappear, usually at times like walking home from school or similar, and then a few weeks to months later, would turn up dead. There wasn't really a pattern to where the bodies were being found, and the injuries varied a little, but were all pretty massive trauma, if of the sudden sort. They were all boys, mostly similar hair color.
Saguru'd basically insisted on getting into this even though a lot of the Yard didn't really want him on it - he was around fourteen at the time.
He managed to track it back to a single mother who'd lost her son in a drowning accident, body never found; she'd snapped and started taking other children, basically gone delusional to thinking they were her son. Of course, the kids generally didn't take well to this and were usually panicking and freaking out, which would sooner or later trigger a snap and her lashing out; she was pretty much stuck in a mental loop and very broken. He ended up with some nasty bruises and very nearly getting a few new injuries since he ended up snagging the most recent kidnapping during one of her outbursts - he was supposed to wait for backup, but when she turned violent, he dashed into interfere before they got there.
This was the first case where he got taken out drinking with them; it'd been a pretty traumatizing case all around, and the Yard was going to go out drinking afterwards to get away from it... and not only realized it'd be kind of cruel to leave Saguru basically by himself at the station after that, but concluded that if he was old enough to risk his life on a case like that, he was old enough to go out for a drink afterwards to get away from it.
There's some kind of currently non-detailed case that happened in Munich around Oktoberfest, which was the only time he'd been in the city for the festival.
He has at least a couple of other fairly high-profile cases in Europe, enough that while the Cardiff case had drawn plenty of attention, his reputation got cemented as actual ability more than just one fluke.
****- He did have some fans before he got on the Kid case, and there were occasions where reporters had learned that keeping an eye out for him was a good way to end up finding SOMETHING interesting, which only meant him getting MORE noticed, and that some cases of his that weren't that "spectacular" technically got international attention.
The comedy was that his relationship with classmates tended to be as lousy as ever; if anything, some of the more hostile ones were more inclined to razz him for being "the big-shot detective". He kinda loathes his own age group most of the time. He tended to be very confused and slightly skidged by having -fans- and generally avoided them.
{KAITOU KID}
The first few Kid heists he heard about he ignored; he took a look at what was mostly known of the record, deemed that Kid was, in the end, nothing worse than a public nuisance, and went back to focusing on his other work/classwork/books.
And then Moonlight Eye happened.
It was half coincidence that his attention got pointed to the news reports on the case, and he had a small "wait wait go back" tweak at noticing the number of small differences between the Kid who'd been running that heist and the ones before it,and the Kid who made the getaway - shorter, one had a mask while the other'd returned to the monocle and charm, etc.; the realization that there were at least two Kids raised a number of other questions and put the case in a whole new light. He dug up a bunch of information on the case, compared videos, and generally pored over it for clues, and worked out some things in overview from the history of the case and some of the recent heists -
That there had been three "Kid"'s over the history of Kaitou Kid;
That there was some other unknown party they were reacting to;
And that the first Kid was probably dead to said unknown party, with the middle, less flamboyant Kid probably being an ally or assistant/other accomplice, while the new one was probably a child or apprentice to the first - more likely the former.
Then he went down lists of possible suspects, and noticed that there was a correlation between a couple things with Toichi - that all the first Kid's heists had been within at least an hour or two travel-time of Toichi's location where both factors were known, the first Kid slowed down and suddenly was working in a more limited area when Toichi had a family and was in one place more, and the change between the first and second happened at the same time as Toichi had his "accident"...
And both the subsequent Kid's would be in the area and timing range for certain people around Toichi, which pointed at one solid suspect for the new Kid.
Notice that he transferred into Kaito's class the day after the first heist he attended - and considering that school transfers take some paperwork and time, it had to have been arranged before he even went to the heist.
It'd be lying to say that he wasn't interested in being the one to catch Kid when he started out; he DOES have an ego and it WAS a pretty large challenge dangled in front of him. Of course, there was also that ulterior motive that he knew there was some other, worse group Kid was trying to bait, but in the beginning his motives were a little split and he'd actually had the assumption catching Kid and them weren't mutually exclusive.
As time went on, two things happened. One was that as they started popping up and reacting to Kid, he got a better idea of the negative space tracings he had and what Kid was up against, and started to realize that they had outmaneuvered and flaunted legal authority enough that Kid being caught would probably be a death sentence, and probably mean losing his only real lead against the worse criminals. The second was that he did get attached to Kaito and Aoko. Of course, having a clue what they were up against meant that he knew that changing his behavior drastically, particularly with how visible to the public eye he was, would be suspicious and draw their attention, so he kept up the usual dance and game and played up being obsessive about Kid to justify the extent to which he was NOT getting involved in his more serious work.
It also did occur to him that the places where he'd been interjecting into heists as "the best chance to catch Kid when he's not expecting opposition" were also ideal places for an assassin to strike out of view of the law enforcement chasing Kid, and therefore, he had every reason to continue that even if he didn't have any intention of getting Kid arrested.