Very authentic South American cooking - the spicy, garlicky shrimp soup (with rice and green peas) was amazing, and the Aji de Gallina (stewed chicken) is definitely worth a try. Spanish-language ability helps - they don't speak much English or Japanese. Inexpensive.
This book will introduce you to more than twenty of Japan's favorite specialty foods that are less well known abroad, along with a guide to the best places in Tokyo to try them and expert tips on what to order. From Bento.com.