are you talking about this city of beast? http://www.amazon.com/exec/obidos/tg/detail/-/006050918X/103-8935470-6475813?v=glance
well,the leading guy in the story alexander,meets this girl named nadia, they end up being close,they become best friends,but in the ending they get separated coz alex has to go back home,and nadia stays in the amazon. i just think it's sad getting separated from a friend. especially when she's your best friend.