Congrats for winning as Reimu! Y'see, it's a pun on the Remington shotgun but we add "Reimu" to it, also the 890 when read separately in Japanese sounds like Hakurei. It's a reference to a Youtube video by the same name, give it a watch

Congrats for winning as Marisa! Y'see it's a reference to the M4 carbine rifle but then we sneak in "leet" speak to spell "Magic". Yeah I spent a lot of time on this

That's what you get for trying to take pot shots while she's stopping time! And yes, this is a Jojo reference