Cave Story (Dokutsu Monogatari) is described as 'Cave Story, or Dokutsu Monogatari, is a Japanese freeware Metroidvania side-scrolling Metroidvania platform-adventure game developed by Studio Pixel . It has been translated into English by Aeon Genesis Translations' and is a Platform Game in the games category. There are more than 25 games similar to Cave Story (Dokutsu Monogatari) for a variety of platforms, including Windows, Steam, Playstation, Mac and Nintendo Switch apps. The best Cave Story (Dokutsu Monogatari) alternative is Hollow Knight. It's not free, so if you're looking for a free alternative, you could try Castlevania The Lecarde Chronicles or MegaMan Unlimited. Other Cave Story (Dokutsu Monogatari) like games are Celeste, Castlevania, Ori and Blasphemous.
It's got wonderful pixel graphics, great platformer feel and shooting very similar to Cave Story. The world is a weird, fantasy mixed with sci-fi, yet colorful and lovable. Interesting story and bosses.