The universe of the show that you three have entered is: Oshi no Ko!

One day, the three of you were walking around the apartment complex in which Ai Hoshino resides with her children: Aqua and Ruby. Suddenly you three noticed a man standing in front of her door in a black hoodie. That man was Ryosuke, her obsessed fan.

Josuke: "Oi, I think that's the guy that's about to try and kill that idol girl."

Okuyasu: "You're right, he matches the description. That's definitely the dude who killed that purple-hair chick."

Josuke: "Then what the hell are we waiting for? Let's go!"

Josuke activated his stand, Crazy Diamond, and Okuyasu activated his stand, The Hand, before all three of you rush towards Ryosuke to intervene.

Meanwhile the stalker was talking with Ai, who seemed wary of his appearance understandably so. His hoodie covered his face and the knife was concealed within the bouquet he was holding, waiting for the perfect time to stab Ai after learning she had children.

Ryosuke: "Congrats on your dome concert. How are your twins?"

The twin children behind her, Aqua and Ruby, were scared and wary of the man, sensing his intentions. Unbeknownst to this obsessed stalker, you, Josuke, and Okuyasu were going to beat the ever living crap out of him.