It's about Touhou 12. The UFO ship is called the Takarabune ingame, IIRC and I've seen theories online about how the UFO crew paralel the seven immortals.
UFO happened. It got a ship the main characters calls Takarabune (or Treasure Ship) where the UFO crew (minus Kogasa and Nue) belongs, where one of them is the disciple of Bishamonten.