Your Heart Is a Little Warm

The heir to a declining martial arts family in the 21st century was inexplicably stabbed with a needle while walking on the road, and a strange box was stuffed in it. He was hunted, ran into an apricot forest, and traveled to an overhead parallel world, the Monsoon Continent. Unfortunately, something went wrong during the time travel, and he turned into a child. He accidentally saved a dying prince, and the story unfolded...