5億年ボタン

The story centers on a button that grants a million yen to whomever pushes it, with the condition that they must spend 500 million years alone in an empty space. However, at the end of the 500 million years, the person's loses that memory and returns to the point in time when they pushed the button. A person with this button appears in front of 5-year-old Tonio, 14-year-old Jaibi, and 17-year-old Suneko - three siblings who need money to pay for their father's hospital treatment.

(Source: Anime News Network)