Final answer:
The character Mowgli first appeared as an adult in 'In the Rukh' and then as a boy in 'The Jungle Book', both written by Rudyard Kipling.
Step-by-step explanation:
The Kipling character that first appeared as an adult in the story "In the Rukh" and then as a boy in "The Jungle Book" is Mowgli. Rudyard Kipling's works often explored themes of adventure and nature, and Mowgli is central to these themes. Mowgli is known for being raised by wolves in the Indian jungle and has adventures involving various animals such as Baloo the bear, Shere Khan the tiger, and Bagheera the black panther. The stories of Mowgli in "The Jungle Book" and its sequel "The Second Jungle Book" are among Kipling's most famous works and have been adapted into various media over the years.