Sumireko Usami is a human from the outside world dealing in all sorts of psychic powers. She's a highschooler. She's the first president of the Secret Sealing Club, which mainly investigates the existence of other worlds, including Gensokyo and the Moon. It's also the club where two of my most beloved touhou characters (Maribel and Renko) belong to, albeit in a different timeline. She's the perpetrator behind the Urban Legend in Limbo incident- Temporarily using her powers to enter Gensokyo as a