In Japanese, the term Daikoukai Jidai refers to the period between the 15th century and the 17th century, when European explorers sailed the seas to open new alternative ways to Asia when the Ottoman Empire blocked the land routes.

This period was characterized by the rivalry between Spain and Portugal, the advent of colonization, and general exploration. In later games, other countries are also involved. Some historical events during the Age of Exploration, like the Treaty of Tordesillas, were mentioned.

The game series makes many references to the historical background, although much like Pirates!, the more treacherous details of the era are idealized to create an adventurous and exciting mood.

In the first game of the series, the player assumes the role of Leon Franco, the young, ambitious son of a noble family fallen on hard times in Portugal. The goal of the game is to restore the family's former glory and achieve Leon's dreams. Only three nations are represented, Portugal, Spain and the Ottoman Empire, although there are many neutral ports around the world that the player can "invest" in and thus make part of Portugal's sphere of influence. This, as well as discovering ports and defeating other merchants and pirates in sea battles, increases Leon's fame. With increased fame, Leon can complete tasks for the King of Portugal and gain higher titles of nobility.

The story is set in the early 16th century. It was released on MSX and NES in 1991, and Sega Mega Drive/Genesis and SNES in 1992, with the SNES versions known as Super Daikoukai Jidai in Japan. The English versions were also released in the same years respectively. The game was ported to PC, as well.

Known as Daikoukai Jidai II in Japan, this game is perhaps the most famous of the series. Even though an English version exists, it still has not managed to achieve the mainstream popularity Pirates! had. There is only a relatively small following outside of East Asia.

Also set in the 16th century, this game is a sequel to the first title and was released for NEC PC-98, SNES and Sega Mega Drive/Genesis in 1994. It was the last part of the series to be ported for PC. It also saw releases in 1996 on Sega Saturn and PlayStation in Japan exclusively. The SNES version recently appeared on Nintendo's Virtual Console in Japan on March 17, 2009 and in North America on April 6, 2009.

In this game, there are six protagonists to choose from, each of them representing a different path or career featured in the game. They are listed as follows:

• João Franco: Son of Leon from the first game, a Portuguese explorer sent by his father to follow the family's footsteps and discover the secrets of the lost continent of Atlantis.
• Catalina Erantzo: Former Spanish naval officer turned pirate, she avenges the loss of her brother and her fianceé and suspects that the Franco family is behind this scheme. She is loosely based upon the historical character of Catalina de Erauso, the Lieutenant Nun.
• Otto Baynes: English naval officer, a privateer sent by Henry VIII in a secret mission to defeat the Spanish Armada and prevent Spanish hegemony in the European continent.
• Ernst von Bohr: Dutch teacher and cartographer, he is set to make a journey to far lands and with this experience create a map of the entire world.
• Pietro Conti: Italian treasure hunter, he inherited a huge debt from his father and is set to travel for treasures and other secrets in order to cover the debt.
• Ali Vezas: Turkish merchant, he grew up as an orphan in extreme poverty. With the help of his friend, he decides to become a trade merchant and find his lost sister.

While the game is more or less open-ended, developing the character's career is necessary to advance the plot.

Mobile Uncharted Waters II

In 2007, Koei announced the release of mobile daikoukai jidai 2 (English: Mobile Uncharted Waters II) [1]. The game is a port of the original game for both iMode and Yahoo Mobile capable mobile phones in Japan.

Released in 1996 on PC, this title was the first to depart from the formula and engine of the series. The traditional focus on story was removed in this game, and some character customization is possible, if only purely decorative. There are two player characters from Portugal and Spain. Although the differences between them are mainly mechanical, the role-playing element was greatly reduced.

The theme of exploration is heavily emphasized, as land travel is now possible, and there is a lot more to be explored and discovered overall, compared to the early titles. The game starts in the mid fifteenth century and allows for the player to make historical discoveries such as the New World or a route to India as well as conquer civilizations like the Aztec and Inca Empire. Also, the game experiments with the concept of language in a video game, a feature uncommon in the industry, and necessitating the hiring of translators and teachers. The player can also continue the game by marrying bar-girls and having children, who in turn can continue the seafaring tradition and even take on part of his father's skills and inventory. Perhaps it is due to these dramatic changes that Daikoukai Jidai 3 left players uncomfortable and failed to achieve much popularity even within Japan.

At its initial release, this title caused some controversy for allowing slave trade in the game. The feature is disabled in later updates.

Unlike most games in the series, this game was never released for consoles; it was only released for PC, working under Windows 2000.

A side story released in 1997 on PlayStation and Sega Saturn after New Horizons, the game uses the same engine and focuses on the story of two characters instead, further expounding upon the loose plot that ties the series together. The two protagonists are as follows:

• Miranda Verte: Genoese adventurer who mistakenly thought the treasure hunter, Pietro Conti, had asked for her hand in marriage, and sets off to find him. Her quest eventually leads to a plot relating to an ancient civilisation in South America, which were touched on by Pietro's previous adventure.
• Salvador Reis: Pirate and adopted son of Hayreddin Reis (aka Khayr ad-Din). His adventure involves rising to fame as one of the Algerian pirates, compete for domination with enemy pirate clans and also struggle for power within his own clan.

The fourth game in the series was released in 2000 for both PlayStation and PC under Windows 2000 and XP. This game returns to the previous formula, although its open-endedness has decreased and the engine has been updated. This title is plot-wise unrelated to the series that ended in Gaiden. Porto Estado is known for its fine art and high-quality illustrations.

The story evolves on the search of the seven Proof of the Conqueror, which are seven ancient artifacts, in seven areas around the world (Northern Europe, Mediterranean, Africa, New World, Indian Ocean, South Asia and East Asia). It is said that having these proofs proves that the sailor is the champion of all sailors. Four sailors (plus another three in expansion) unwittingly involved in the struggle of the quest of the search of the Proof of the Conqueror. It is interesting that not all sailors are from Europe: two of the seven characters are from Asia (one from East Asia and another from southeast Asia), one from Caribbean and another one from Middle East.

There are many significant changes in this game. For example, the game no longer has the concept of year and the result is that characters in this game will not age. Also, player can set up regional fleets and these regional fleets are valuable financial resources. In combat, naval battle is now fought in real time.

The country boundaries have disappeared. Each character is only represented by their own guild and their home country is not important in gameplay. Ports in this game also have a market share rating in a percentage scale. Players can trade in a port only when his guild has some market share in that port, which can be gained by signing a contract with the local governor.

Daikoukai Jidai IV: Rota Nova

Rota Nova was released by KOEI on March 23, 2006 for the PlayStation Portable and Nintendo DS. This is a remake of Porto Estado for handhelds:

• The PSP version includes a ship race function.
• The DS version includes use of the stylus and map.

Uncharted Waters Online offers much of the same gameplay experience seen in the single player games in a multiplayer environment. Players of the single player series will be well aware of similar concepts such as Missions, Adjutants, Investment, and National & Pirate NPC fleets.

Country boundaries have reappeared, with more countries (Spain, Portugal, Venice, Ottoman Empire, France, England, and The Netherlands), however the concept of time is non-existent. The storyline is important to unlocking new areas in the game. The player now receives fame from activities such as battling, trading, discovering, and sailing. When fame levels reach required amounts, the player unlocks new areas of the world. The level of fame required differ from country to country.

The game introduces a 3d-environment with DirectX 9.0c capabilities. As any MMORPG the game features fleet operations (party-system), companies (guilds), player versus player combat, trade, adventure, and poker, and large-scale factional warfare. As well, the game offers a single player storyline and player-vs-environment quests.

The soundtracks for both Uncharted Waters and New Horizons were composed by Yoko Kanno. The soundtrack for Uncharted Waters Online is based in part on those works.