In case anyone else is curious/nitpicky, this doujin somewhat blends together the Touhou use of bourei/yuurei (ghost/phantom) as specific types of spirit, and the more generic Japanese use of yuurei as just whatever "spooky spirit that scares people". I chose to interpret that on the first page, when Yuyuko says 幽霊 in kanji, she means "I wanna become a phantom because clearly being a ghost isn't working", but the rest of the time, when she says ゆーれー in deliberately simplified hiragana, she's already moved onto "spooky spirit that scares people".

On an interesting side note, usually when Youmu gets scared of "ghosts", she's actually not talking about either bourei or yuurei but simply obake, which as far as we know doesn't have a specific meaning in Touhou terms. So she's one type of spirit, living with another type of spirit, who is deathly afraid of a (possibly non-existent) third type of spirit that shows up in ghost stories.