[X] Inform the SPW directly that you believe there to be dangerous Stand activity. You don't know the details, but were informed that knowledge of this kind of thing was their specialty. Perhaps there is something they can do to help?
Your mother might have wanted out of the world of the Supernatural, but she wasn't going to leave her child in the dark. She told you what you needed to know in case things started to turn ugly. One phone call and a pass phrase later and you're talking to the Speedwagon Foundation Supernatural Research Department. You tell them about your encounter with Thomas, the murder by arrow on the news, and your general suspicions. You're call is soon forwarded to a third person.
"Hello, this is Lawrence Shaw. I was given the bullet points before your call was transferred. I'll be frank, Joshua, we suspected something was amiss when we heard about such an unusual murder weapon, especially in an area hosting two heirs to the Jostar bloodline. Your report seems to confirm our fears; that someone in your area has gained possession of a Stand Arrow. Unfortunately, our capacity for direct action is limited. As powerful as we are, the Speedwagon Foundation is a private entity, not a legal one. Even if we were, whoever has the arrow is almost certainly a Stand user themselves, so us normal humans will likely be powerless against them. However, we are not powerless. We have plenty of connections with underworld, primarily information brokers and related groups. We will make sure to keep you posted on information as soon as we acquire it." Lawrence pauses for a moment, before sighing heavily. "As much as it pains me to do this... we may need your help. Our records show the tests Ms. Kujo brought you in for, we know all about your Stand. As today's events showed, you will be roped into this, regardless of what you desire. However, if you go forth willingly, maybe you can do more to control your fate. I can't make you do anything, but here is my offer. We will supply you with information about strange occurrences in your area that may lead you to other Stand users. Try your best to either recruit or interrogate them, neutralizing them if needed. Hopefully this will lead you to whoever holds the Arrow. I won't lie, this is dangerous work. Stand Users are prone to violence, considering Stands are manifestations of the will to fight. But as a Stand User yourself, you're bound to face them eventually. The choice is yours. Take as long as you need to decide."
[ ]Hunt the Arrow
[ ]Refuse
[ ]Contact them at a later date
[ ]Write in
So ends the prologue. Your choices here and in previous posts should be enough for me to include more dialogue and action, since I'll have a better image of Joshua and I won't have to consult you guys for everything he says and does (though plenty of decisions still go to you, and Joshua can change over time).
Also it has just occurred to me that this takes place in 2030 at the earliest, whoa. Things probably won't have strayed too far from the modern day, though tech can be assumed to be functionally better while practically the same (higher definition, more durable, stabler connections, all cheaper). It's just more manageable for me this way.