The patcher will ask you to select your data.win file and the provided .patch file.
: An unofficial "demake" specifically designed for 3DS resolution. undertale ds rom download upd
: A dedicated Nintendo DS port that recently reached a playable state for the first 10-15 minutes of the game. It requires users to provide their own data.win file from a legal Steam or GOG purchase to build the ROM. Undertale-3DS (CooingMaxito) The patcher will ask you to select your data
