Uboa is an enigmatic antagonist in Yume Nikki.
Uboa is a strange creature, usually considered male or genderless. Contrary to popular belief, Uboa may actually be female due to its eventual replacement of Poniko's sprite. There is a chance that it will replace Poniko when you turn off the light, and plays a continuous muted "aaaaaaah" sound, (if properly filtered) surprising most people.
When the event happens a bright flash fills the room, similar to a blowing light bulb, then the entire room changes and Uboa replaces Poniko (if you kill her before triggering the event, Uboa is not going to appear.
However, you will be locked in Poniko's room). You cannot leave the room, and flipping the light switch only causes another flash of light. If you touch Uboa, you will be sent to a Monochrome Street highly similar to the White Desert (with even its soundtrack playing).
Which is a looped area flooded with white liquid (potentially a swamp or marsh), a strange monster in the background bleeding , and Uboa's face will become strangely warped. Despite this location's atmosphere being identical to the White Desert's, there are no routes that lead away from this area and into the White Desert itself.
The only way to escape Uboa's Trap World is by pinching Madotsuki awake or by using the Medamaude effect.
- When the Uboa event activates, some of the items in the room change. The dresser gets a "face" with googly eyes that may remind players of those of Masada and what seems to be a creepy smile. The two pictures change, the one over the desk turns from what looks like a mouse to a face which has googly eyes as well, and what could be either a moustache or a creepy-looking smile, and the one over Poniko's bed that changes from one shape to another. The window gets eyes and the rug's design also changes, showing a pattern with eyes as well. The lamp on the desk turns on, showing a light beam.
- Uboa has been one of the most popular characters from the game. Uboa has also made cameos or inspired for other characters in some fangames.
- Yume 2kki - In the Sky Kingdom world there is a dog-like character that resembles Uboa. This character has been called "Dogboa" by fans.
- .flow - Uboa makes a cameo as a marking in the dead end room in the Underwater Temple.
- Me - the Mask effect is a clear reference to Uboa's face, and the location it's found in is quite similar to Poniko's room.
- Uboa has, strangely, become a meme, despite it's only appearing ingame one way.
- Uboa might have inspired the Hollow from Bleach (or the other way around) as he and some Hollows look very similar.
- According to some, Uboa's design (that of its initial sprite) was likely inspired by Spirited Away's No-Face.
- Uboa's name originated from a type of scream in Japan. Originally pronounced 'uhoa' (ooo-hwha) when said in a manner resembling a scream, the name certainly suits its appearance and situation.
- The origin of Uboa's face design prior to its distortion when the player touches it may have come from a 1997 Treasure game called Mischief Makers. This may be coincidental however. In Mischief Makers, the denizens of the planet Clancer as well as most objects on the planet all have black, hollow-looking eyes similar to Uboa's that may be both curved inward or one curving outward. These creatures also possess gaping black mouths and white faces, much like Uboa.
- In the walfas' create.swf (despite being Touhou in origin but because of Uboa's meme status) Uboa's face is an option to use on a character.
- In Undertale, a door may show up in one of the areas that leads to a creature with a striking resemblence to Uboa.
- Whiteface from ImScared vagualy resembles Uboa.