Sumireko is actually a genius character and ZUN definitely knew what he was doing. See, she's not one like the hardworking miko or the ass-kicking magician. She's a zoomer who visits a magical place in her dreams without paying rent. She visits, rent-free, to the place that's shrouded in secrecy. And she does it with such glee, even going as far as to demystify Gensokyo by sharing the magic to her Instagram for outsiders to see. She is the perfect representation of an unwanted tourist, which is a good reminder to all Touhou players of what lies beyond the CAVE we inhabit.