The game tells the tale of the Birth of the Island Nations and the story of the Rune of Punishment. It is set 150 years before the first Suikoden game. This was the first entry made without any known input from series creator Yoshitaka Murayama. Instead, creative duties were given to his long time collaborator Junko Kawano who took over the series after he left. Suikoden IV was the first entry to use voice acting and was designed to work with Progressive Scan TVs. It was followed up by the side story Suikoden Tactics.
Suikoden IV is a traditional turned based RPG like previous installments. Players control a party that explores dungeons and towns while completing quests and battling enemies. The purpose of the game is to collect the 108 Stars of Destiny while exploring the world.
Suikoden IV breaks from series tradition and reduces the total active party from six to four. Though, when you are traveling on the Dauntless, you are given the ability to create two additional teams of four that can be switched to during random battles on the ship. The game also introduces the Rush command which has your whole party pool their strength together to heal the leader of the party and unleash a powerful group attack without taking up the party's turn. After Rush has been used, it is inactive until your party wins a certain number of battles. Suikoden IV also does away with Suikoden III's Buddy System and Skill system, instead returning to the more straightforward systems of Suikoden I and Suikoden II. The game re-introduces the Rune Piece weapon system from the first Suikoden and alters the Unite attacks by making players fight a certain number of battles with the proper characters before unlocking the Unite Attack; another new addition is that Unite Attacks can be leveled up if they are used enough times.
The Duel system also returns and largely plays the same as previous installments with its rock/paper/scissor mechanics. Instead, the game alters the cinematics of the duels, allowing for more stylized choreography thanks to the game incorporating more complex movement in character animation and the use of motion capture.
Army Battles are altered from previous games to incorporate the game's naval setting. Players now control ships armed with Rune Cannons. The player chooses a Captain who affects movement and defense. Party members with elemental runes can be assigned to the Rune Cannons and designates what type of Rune Shells the ships fire. The type of shells play an elemental rock/paper/scissor mechanics due to ships having the ability to counterattack while being attacked. if both ships use the same elemental type, the attacks cancel each other out; if they use elemental types that are not weak to each other, both ships will be struck. If the one ships fires a shell which has an elemental strength over the other ships, it will neutralize the weak shell and strike the ship. The last section is assigning members to help with boarding a ship. Certain party members get more underlings than others and increase health for the ship, but more underlings also affects the ship's speed and lowers the amount of turns they get. Balancing speed, defense, and exploiting elemental weakness is important when deciding how to set up your ships.
Other changes in the game come from the introduction of a item crafting system in where the player can buy raw materials from Trading Posts or materials dropped from monsters, and have the ship's blacksmith/Tailor/Accessory Atelier build new armor and equipment for the player. Trading posts have also been slightly altered by the introduction of the materials, and frequent trading will unlock higher grade versions of material which can be used to build better armor.
Suikoden IV is also the first entry in the series to not give the player bonuses for having a save from a previous Suikoden entry. This may be due to the game ultimately being a prequel to the first three games. A Suikoden IV save file does net you bonuses and extra party members in Suikoden Tactics.