Tasei's Kid is a water creature that can be found in the lake of Witch's Island. It has a single red eye and green snake-like body. There has 1/16 chance it will appear in the lake each time you enter the screen.
Interaction
Like other water creatures, it cannot be reached and only reacts to the Cat effect. Interestingly, it has a sound effect set to play when interacted with even though it can't be reached, which seems to be Unused Content.
Trivia
Tasei's Kid is also known as Mars-Sans child or Mars-Sans son, due to the theory that Mars-San is its father. This theory came about due to their similar appearance, though this may be purely coincidental due to the fact that players cannot see Tasei's Kid's lower half, and that is a major defining feature of Mars-Sans design, as he was based on the surrealist painting "Person throwing a stone at a bird" by Joan Miro.