From
https://kuniokun.fandom.com/wiki/Downtown_Nekketsu_Story Story
Dnm plot
Conversation between Kunio and Riki prior to the beginning of the game.
Several months after Kunio defeated Sabu and rescued Hiroshi, twin brothers Ryūichi and Ryūji Hattori transfer to Reihou Academy. Within a few months, the brothers take control of the neighboring high schools using powerful fighting techniques, striking fear as the "Double Dragon Brothers". Riki, the banchō of Hanazono High School has no interest in the brothers or what they have been doing. But one day his girlfriend Mami goes missing and he receives a challenge from the academy. Enraged, Riki decides to make his way to the academy alone, but finds Kunio waiting for him outside his school. Kunio wants to help Riki rescue his girlfriend and he begrudgingly agrees.
Gameplay
Dnm mode
Mode select screen from the Famicom version.
Up to two players can play through the game together in two separate modes, one with friendly-fire (2P Play A) and one without it (2P Play B). Either player can play as Kunio or Riki, who play in exactly the same way. In a single player game the player can choose to play as either character, which changes the in-game dialogue (dialogue in a two-player game will prioritize the first player). The game has three difficulty levels: Easy, Normal and Difficult. Easy will decrease the stats of each enemy and boss by 16 and Difficult will increase their stats by 16. The speed of the in-game text can also be modified. Pressing the Select button at the mode select screen allows players to rename their character.
Dnm gameplay
Gameplay in the Famicom version of the game.
The game's style of progression is that of a role-playing game. The game has no actual stages, instead the player is able to travel in an open world in a sandbox manner around nine different areas. In most of these areas, Kunio and Riki will be attacked by rival school gangs. They are identified by their colors, different AI fighting patterns and the money they drop. The farther the player moves from the starting area (Hanazono High School and the neighboring Hanazono Town and Shopping District) the tougher enemies become. Each gang has nine enemies which are distinguished by their faces and stats (each enemy represents a different stat).
The objective of the game is to reach Reihou Academy (River City High in the western versions of the game), rescue Mami and defeat her kidnappers. Players are free to do as they wish during the game, but until they defeat the Shitennō (四天王 "Four Heavenly Kings") of Reihou (The Zombies in the western versions of the game) they will be unable to gain access to the academy. Since the player can go wherever he wants, it is possible to skip combat by running away from enemies into another screen. In some areas, only four enemies will appear and when they are defeated a boss will appear. When enemies and bosses are defeated they will drop money that the player can use at shops. Bosses can also be fought multiple times.