Alright, you've decided; family and goals are what you're looking to find out, for now that is. It'll give you a better look at his character beyond 'Self-serving Chaotic Neutral who's a friend of Shirou's. Also likes magic'. After all,
most teenage boys would rather woo women and generally do fuck all rather than risk their lives in a dangerous underground secret cabal war. Sure give em a year or two and
then they'll be racing towards that shit guns a'blazing, but now? Nah, still too young for the standard 'adventurer's call' to actually reach them; barring some exceptions of course.
The moment you enter the Matou estate, all you see is chaos; an endless sea of papers, books, and scrolls cover every possible surface you can see. Plates with half-eaten food stand as islands within the sea of texts and notes, scattered throughout without rhyme or reason; all only grazed on at best. And in the center of it all was Shinji, pouring over a scroll and looking back on the spellbook you gave him; bags on his eyes and with unkempt hair, you can tell that he hasn't slept at all since the moment you gave him that tome.
You try to get his attention away from the book and onto you, "Hey, kid! We need to talk."
No response, he's still focused on the tome; "Hey, Shinji!"
Still nothing, "Shinji!!"
Nope, not a twitch;
"HEY DUMBASS!!!!"
That finally snaps him out of it, he jolts up and notices you, "Wha? Huh? Oh, it's you. Hey-" Shinji yawns, "ahhh, whaddya need?"
"Well, I kinda realized that I forgot to talk to you about some stuff so I came here to get answers," you shrug and say with a rakish grin, "you know, cause we're partners now and stuff. So let's start with your family; what do they do, what's their history? You mentioned a grandpa...?"
"The Matou family is one of the three founders of the Holy Grail War, and normally has a representative participate in the war. However, we've been in a decline; our magic circuits dying out, to the point where I have none. I, the family heir, couldn't perform the family trade..."
Shinji's face darkens, and his voice becomes bitter and scornful, "
Grandfather never considered it worthwhile to actually
tell me that though until it was too late, just letting me waste and squander my hopes and dreams for his own sadistic amusement. The one thing I had always dreamed of doing, I learned I could never do. If I could, I'd kill the decrepit bastard; though I'm sure he'll croak any day now, he's more a living corpse than an actual person. Always has been; whatever time he has left isn't long, and I'll be glad when he does finally die..."
That was rather informative, Shinji just became a little more useful; and trustworthy. Guy just wants to prove himself and fulfill
his dreams, despite them being impossible. Not his fault his gramps is a total asswipe.
Then you ask the kid, "And you goal; your wish and the reason for you going into this war is to prove yourself, right? At least, that's what I'm guessing here."
Shinji sighs, and rubs his eyes and says, "It was, but now? I have magic now, thanks to you; and while I still want to show them all how wrong they were, I don't actually
need the grail for it anymore. Speaking of magic," he pulls out the tome you gave him, "You got any more of these?"
That was a little out of left field, "Umm, no. Sorry, any other tomes I had were all in my ship; and I don't have that anymore."
Shinji smiles and then says, "Well, I guess I have a wish now; getting you your ship back for more of these." He holds up the tome.
"Oh, uh, thanks man," wow, that's actually kinda nice of him; despite being done for more selfish reasons, "So, besides the asshole of a grandpa, any other family?"
"A sister, adopted, her name's Sakura; but you should already know that. She practically lives at Emiya's place, though she wasn't there today...I think..." Shinji scratches his head, trying to remember more than what he's been reading.
"Does she know about the whole magic family thing too?"
"No, not a thing." A lie, you can tell that right off the bad; and it's a little odd that Shinji, who can't use magic, could summon a Servant...
Hmmm...."What is she like, personality wise? Confrontational? Passive? You know..."
"Passive, definitely; avoids trying to cause trouble for anyone and rarely confronts anyone." It was actually Shirou who pitches in there, probably still digesting what he's heard about Shinji's family.
Shinji nods in agreement, "Yup, Emiya's nailed it right on the head there."
And like that it all clicks in place; adopted kid is obviously for renewing the family line, happens with noble families with fertility problems. War comes along and the chosen heir doesn't wanna fight; not their style or in their blood. So instead, get a patsy to do it for you; better yet, someone who
wants to do it in your place. Everyone wins. It's actually more common that most would think; wizards getting others to do their dirty work for them, just focus on the summoning spells and necromancy, get some fighter meat-shields, and all the wizard has to do is sit back and enjoy the benefits. Lazy bastards.
Suddenly, you hear a roar and thunder echoing all around; rushing outside the four of you find a enormous serpent with radiant silver-white scales, horns like a stag, and vast wings akin to a dragon's. It's limbs a mix of that of a eagle's and a tiger's; or any great feline really, and with whiskers on it's snout like that of a rat and encased with golden armor that's solely ornamental above all else; it's a sight to behold.
Reaching in it's breastplate, it pulls out a envelope and hands it to you; then lays down on all fours, waiting for something. Hesitantly, you take the letter and open it; inside is an...invitation...
Tandem the Spoony,
You and up to four guests of your choosing are cordially invited to:
A Feast of Kings and Heroes
Hosted by the Sacred Trinity two days from now, upon the eve of twilight at the Fuyuki Church
RSVP with a written response and send it with the messenger dragon ASAP
P.S. We hope that you may regale us with entertaining tales of your heroism and prowess; also, Gil's raring for Round 2.

-
C
Wow, ok. You immediately write up a reply that you'll be there and give it to the dragon, who takes it and flies off. Apparently your one night out has paid off and gotten you an in with some
really powerful people.
But back on the earlier topic, "Hey Shinji; since your family does thing with the whole circuit thing, can you do something to open them up? I think Shirou's got some and since he's balls at Vanacian Magic he might do better with your magic." You snap your fingers in front of a shell-shocked Shinji to snap him out of his awe.
"What? Oh," he thinks a bit about what you said, "Yeah, gimme a sec." With that, he races back into the house. Several mintues of waiting later he returns....
...With a dickworm. No, seriously; it's a worm shaped like a penis. Holy shit, you have no words.
Seaweed head tells you, "He needs to swallow this."
Well shit, that blows. Well, you gotta do what you gotta do; "Alright Shirou, open wide!"
"Wait a second; hold on-" Before he can finish, you ram the dickworm down his throat and force his mouth shut, making him swallow the damn thing. Seconds later, his eyes roll into the back of his head, he begins convulsing and foaming at the mouth. Damn, you may have seen some poisons out there do worse, but not by much.
You turn to Shinji with disbelief and ask him, "...And you wanted this?!"
Again, shell-shocked, Shinji replies, "....I'm starting to reevaluate my life dreams and ambitions."
Eventually, when Shirou gets better; you wave goodbye to a still stupefied Shinji and you, Shirou and Rider head off to continue your day and patrol as normal.
On the way back, Shirou gets called over by a friend of his; Issei, if you heard right, who apparently needs Shirou for something at the school. You think, you didn't really pay attention because four-eyes was nagging non-stop like he was Shirou's mother. However, you can feel
something off with the kid who was pinging your 'ambiguously gay' signal on your gay-dar.
[X] Reject the offer
[X] Accept and go with Shirou
[X] Refuse, but tail him
[X] Write-in
Notes: So three year old brats are not good for the creative writing process I have learned; also, most nobility have messenger hawks. Gilgamesh has messenger
dragons. King of Heroes still better than u.