Amazon Gakujutsu Tanken (Expedition Amazon) puts you in control of a team of 4 explorers on an expedition to map and study (i.e.: plunder) the ruins of the Incan civilization. Your team consists of a Medic, a Field Assistant, a Radio Operator, and a Guard. After equipping your team with all the necessary supplies (don't forget the mosquito netting!) you travel to your base camp at the edge of the jungle where you will begin your journey.
You will quickly meet up with many of the hazards of the jungle as you explore, including hostile natives (hope your Guard is a good shot!), mosquitoes, disease, covered pits, wildlife, and more. Each of your team members has an "EL" rating which indicates how close he is to dying. Death comes quickly for new team members, but as your team gains experience by mapping more and more of the Amazon and Incan ruins, your EL rating goes up and your team members become quite a bit more effective at avoiding hazards. You also get an Efficiency Rating "ER" which is an overall score of your exploration completed and loot collected minus your money spent and the number of team members killed.
Once you have mapped a few sectors of jungle you will find some ruins with passages leading underground. Underground is a lot more hazardous than the jungle, as many of the pitfalls you encounter mean instant death if you don't have the proper equipment or your team was not alert. The natives are also a lot more numerous underground as well. But don't worry, you can always replace members of your expedition. Besides, what does it matter if you lost your Field Assistant if the rest of your team is carrying out a bagful of gold and silver?