Arriba y abajo

This book is a follow-up book of 'Lost and Found' by Oliver Jeffers. The same two friends of the first book, the boy and penguin occur in this book also. They do everything together, until one day penguin wanted to try flying. Even after trying various methods of flying with the boy, the penguin was not satisfied. Finally, one day he really found the way. But leaving the boy was not an easy option and the boy too felt he was lost. What did the penguin opted for finally, Friendship or Flying?