>>2402283
http://touhou.wikia.com/wiki/Hakurei_Border
>It is the strongest boundary in all of Gensokyo, with Youkai reinforcing the original work done by humans in 1884. Yuyuko has speculated that not even Yukari could make a boundary of this level (from scratch, on her own). Yet it is not completely impenetrable. Examples of this include various individual people (Reisen, Chiyuri, Yumemi, Maribel, Sanae, Kanako, Suwako, and many others) that have arrived through it as well as entire locations (Moriya Shrine, Poltergeist Mansion, Scarlet Devil Mansion) that have been transported through the barrier.