This page offers a guide on grabbing the Shine Sprite in Episode 7 of Sirena Beach. This area is accessed via the pipe on the roof of the house at the Plaza Square once you’ve cleared Episode 4 of Pinna Park and defeated Shadow Mario back in Delfino Plaza.
Defeat Shadow Mario
Once again, your old advesary, Shadow Mario, has returned and this time, he’s causing mayhem at Sirena Beach. To begin the mission, head up to the hotel and speak to the Manager who will let you in.
As with other Shadow Mario battles, the only objective is to keep up with him while spraying him with your FLUDD and you can score some early damage on him right at the start. He’ll take off towards the stairs and climb to the top floor, stopping as he trys to lure you into a Boo. From here, he’ll run into the left room before running towards the room to the left of the sealed pool room. From here, he’ll make his way into said room so you’ll need to navigate the attic via the top left room to drop into there (Ground Pound the floor tile to the southeast).
From this room, he’ll drop down to the previous floor and repeat his cycle, avoid the Boos he uses as a disguise, keep up the pressure and eventually, Shadow Mario will fall once again, providing you with another Shine.