Russian game developer Edik Zykov is working on an Undertale fan game that, for now, is known under the working title “Undertale 3D.”
Despite that working title, the game will actually be 2.5D, it using sprites mapped to a 3D environment. This is the approach that Zykov took with his previous fan game Yume Nikki 3D.
“Undertale 3D” also will not be a direct remake of Undertale and its story. Zykov tells Siliconera that it’ll be a short, spin-off story of his own creation.
“The story takes the idea of the Underground suddenly making it into 3D one day and things that happened because of that,” Zykov says. “Some dark entity in hte Underground plans to use the power of 3D to get into the real world where the player is, and Frisk has to stop its evil plan.”
At the moment, there’s no information on when “Undertale 3D” might be finished, but you could keep an eye on Zykov’s website for any updates.