Anime Crossover: What If I Were a Two-Dimensional Character?

(A lighthearted, all-action crossover for casual anime fans. If it's not your thing, please don't flame me.) Sixteen-year-old You Ming obtains a Command Spell, becoming a participant in the Holy Grail War. He immediately begins summoning his Servant. But at the same time, his System awakens. The Servant and the System appear together, causing a serious bug! Even stranger, the detective agency he inherited from his parents starts acting weird, too. “Demon Slayer, Muzan, you're so beautiful!” “Fight! Take down that Gillian!” “Aizen! You can't get away!” “Gas is about to blow up again in neighboring Fuyuki City!” P.S. This is a crossover mash-up, set in the late twentieth century.