Come on I know you're curious.
1. Train's parents were killed when he was young, but the killer who did it didn't know they had a kid so more out of pity he took Train under his wing to give him the skills to kill the assassin in the future- like an atonement. The Assassin was Zanguine by the way.
2. Zanguine is the reason Train drinks almost nothing but milk- it tastes good and makes you stronger was the excuse from Zanguine...it worked too well.
3. Though Train would never admit it outloud, Zanguine was more a father-figure to him than any other person, even if he loathes the guy for what he did, he'd consider Zanguine family if he ressurected from the dead and decided to say Hi....but first he'd shoot him in the leg.
4. When Zanguine died Train was raised by a Cronos member and a mayor, Karl, and Karl's house is FREAKING HUGE, it wouldn't be put past Train if he didn't turn out to be a Hittachin-ish brat, uncaring about everyone else but himself, up until he was taken into training and humbled.
5. Train despised Creed even BEFORE Creed killed Saya, he was just really, really, really, really ANNOYING! He was like a fan girl and for Mr. Reclusive Number XIII that doesn't fit well.
6. Saya was Train's first friend/Person he was really close to. Or as far as canon points towards it. He probably got along with a few Numbers like Ash- the Number X before Xiao Li, but officially, Saya was the first friend.
7. Train is an only child and really wishes for a family that's why he has a twisted perspective in his head of Sven being big brother/Daddy, and Eve being little sister/daughter and Train is middle child/Mommy....He Twins then 180's to Tamaki, go figure.
8. Even though Saya dying was a trigger to him leaving he was always a wuss at heart and would refuse to take missions where the boss had a kid, the violence and death just didn't get to him. And if he was sent on a mission and didn't have info and the target did have a kid, he'd leave after taking about about three fourths of the Security.
9. Train's last name is LITERAL AS ALL HELL! Every female cast member, minus Eve and Echidna, probably want in his pants(INCLUDING SEPHIRIA). Can you blame them?
10. Train being an ex-assassin means he is skilled in things necessary for sneaking into places, even though he likes the loud and direct fear inducing approach. He can pick locks and hack into systems if he needs to. He just doesn't care half the time cause it slows things down.
11. Train's favorite thing about being a Sweeper-besides the Freedom- is the thrill of the chase.
12. Train is afraid of bugs, I don't know where this came from, but they freak the hell out of him. But he's the hero so he will cowboy up and kick the shit out of them if necessary- fear be damned.
13. Train is cattish in several ways. Milk, Seafood, likes being lazy in the sun on the roof, his eyes, I could sit here all day really.
14. Train has 6/0 vision in both eyes and has Godlike aim. He NEVER misses...unless you move faster than the bullet.
15. Train has an excellent memory but it's selective, like he can remember unimportant things or really tiny things it would take a master detective to notice, but while remembering that he'll forget something like...the amount of the tab for a cafe.
16. The only reason Train doesn't shoot down Kyoko is because he doesn't want to see her cry, and two he thinks she'll go and cause some sort of damage to the populace that would label her a threat to Cronos.
17. Train died a little inside when he left Cronos because Sephiria treats the numbers like her family since she was specifically born to serve Cronos and he knew him leaving would make her break down and be sad, if only a bit.
18. Train's one weakness is a woman's tears. If you get a girl to cry in front of him and he will crumble at your feet and do whatever you say.
19. Train is very skilled in mellee combat and gunman ship, that's why his gun is the way it is, it can double as a cutting weapon in case he runs out of ammo.
20. Like stated before, Train can hack and has a selective and excellent memory, in other words, HE IS A FUCKING GENIUS. He just acts stupid and puts up a front because it's less work on his part.
21. Train is a master of Disguise, he can whip up something in a few seconds. This once again comes from his training as a Number.
22. If Train was a theif- he could probably rival Dark in skill, but Dark has the upper hand of magic, so that's out. Plus he's a simple man with no concept of value, he'd never steal anything intentionally ever.
23. Train's stomach is bottomless, it's actually the reason he and Sven are so far into debt, because whenever they go shopping for groceries or go to a restaurant, they have to buy for Five instead of three.
24. Train would love to have a pet cat but he's far too irresponsible and he knows it, that's why instead of a pet he's just friendly to any strays that decide to come and give him company voluntarily. But since their pretty much rooted at the moment thanks to Eve, he could probably take care of one.