Mewn is a traditional Yume Nikki fangame. The game uses an item-collection system like that of Yume Nikki, but the game's effect equivalent, Components, are unusable. To compensate, the player is given various tools to aid the collections of these items. The goal of the game is to collect all Components. The protagonist is *. *, a spaceman from the moon who has crashed on Earth. Their spaceship is beyond repair, requiring them to find replacement parts throughout the planet.