Three new locations have been added since Yakuza 3 - a rooftop area, which stretches across a large area of the town; the back streets of Kamurocho, known as "Rojiura" and a third area called the underground (or "chika" which includes the city's sewers, parking lot and shopping arcades. The underground area is also known as "Kamuchika", short for "Kamuro Chika" or "Kamuro Underground".
Each main character also has his own "side-game" or goal that must be completed to earn 100% completion, most of which are related to a trophy.
Akiyama may create a "Friendship" (馴染み, Najimi?) with certain NPC characters by buying them items, or certain shop owners by being a regular customer. These characters will then help out at the start of battles that start nearby, by throwing an item to use as a weapon. Befriending the man at Asia enables the player to pick the kind of girl they want to see dance. Akiyama's other mission, "Create a No. 1 Hostess!" (No.1キャバ嬢をつくろう！, No.1 Kyabajō o Tsukurō!?), is to scout girls for the cabaret club he owns - Elise, opposite the Millennium Tower - and, through dressing them up and training them, turn them into the No. 1 girl at the club. There are three girls to train, and after they become number one the player can choose a final outfit before them, after which they appear as a regular cabaret girl at Elise. A similar challenge was in the Japanese version of Yakuza 3, but was cut from the subsequent overseas releases.
Saejima's mission, "Create a Fighter!" (格闘家をつくろう！, Kakutōka o Tsukurō!?) is to train fighters to compete in, and win, tournaments, within 50 rounds of training. Training involves building up training move-sets, with different actions having different effects. This game can be found at the dojo next to the Children's Park.
Tanimura's mission, "Resolving Police Radio Disputes" (警察無線トラブル解決バトル, Keisatsu Musen Toraburu Kaiketsu Batoru?), is to keep the peace on the streets of Kamurocho; occasionally a report will come through on his radio telling him where to find the incident. The player must then defeat the perpetrator. Each unique case must be completed to "clear" the task.
In Kiryu's mission, "Team Encounter Battle" (チームエンカウントバトル?), various gangs from around town will attack Kiryu, who will have to fight members of the team in order to get to their leader. There are seven teams to defeat.
There are also mini games as well.
The story of Yakuza 4 kicks off on March 1st, 2010, when a gunfight in Kamurocho leads to the death of Hiroaki Arai, the boss of the Kanemura family, an affiliate of Kamurocho's dominant Tojo Clan. This seemingly isolated incident unravels into a huge conspiracy set in motion by forces who wish to control the fate of the entire Tokyo underworld.