An Obariyon is a small spirit from Japanese folklore similar to an imp that will attack travelers by hopping onto their back and demanding that they give them a piggyback.
They will continually increase their weight when doing so while also biting at a victim's scalp repeatedly, if a victim fails to take the spirit to its desired location they either collapse from exhaustion or are crushed by the spirit. However, if one succeeds in bringing the spirit to a desired spot it will leave and bestow a large sack of money, granting the former victim wealth enough to keep them rich for the rest of their life.
They are considered to be a symbol of common fears and struggles found in raising children, with the moral often being that enduring such struggles can ultimately gain a reward (as children were expected to grow up, gain employment and help pay for their parents in later life).