Here’s an overview of the game, via Natsume:
River City: Rival Showdown, known in Japan as Downtown Nekketsu Monogatari SP, will launch this fall for the Nintendo 3DS. One night, Kunio is attacked by two mysterious individuals. On top of that, Riki’s girlfriend has disappeared, and it’s up to Kunio to find out the truth! Kunio has just three days to unravel the mystery, and he’ll need your help to take down all who stand in his way! Take on some familiar faces from the River City games and meet new ones in this fast-paced beat-’em-up RPG.
Today’s localization announcement follows yesterday’s localization announcement of River City: Knights of Justice.
River City: Rival Showdown will be playable at the Natsume booth at E3 2017 from June 13 to 15.