The Grateful Poppo-chan

On his way back from school, Tairadori Nodoka spots a crane in distress and decides to help it. What he did not expect is that, after jokingly telling it to return the favor, it would actually come the next morning to do so! But the one who came is... not that crane?

A Oneshot by the Mangaka behind Paper Braver, Fujichika Koume, which was published in Weekly Shonen Champion's 25th issue of 2016. It's based on a story from Japanese folklore called "The Grateful Crane" or "Tsuru no Ongaeshi" (鶴の恩返し, lit. "Crane's Return of a Favor").