We didn't have to wait long for the suspense to end regarding XSEED's mystery game: it is, in fact, Corpse Party for PSP, and it will be released as a download this fall.
Corpse Party, originally created in RPG maker before being remade for PSP by publisher 5pb, is the story of a group of high schoolers "trapped in a haunted elementary school filled with the decaying corpses and tormented souls of countless children who'd mysteriously vanished from the Japanese countryside years, months or sometimes only days prior."
Even though the game is presented primarily in 16-bit sprite-based RPG style, the premise definitely has the potential to be very spooky, with XSEED promising "decidedly uncensored horrors." In addition, a "3D audio" gimmick adds atmospheric, directional sound.
Check out a trailer above, but be warned: there is some disturbing imagery. Just in case you didn't figure that out from the game's title.