Spelunker, originally created by Tim Martin and published by Broderbund in 1983, was at one point licensed out to Irem so that they could create a Famicom version a few years later in 1985. Spelunker II is the sequel to that Famicom version. Its subtitle means something like "Challenge of the Hero".
Spelunker II was notable for its infusion of RPG elements to the standard Spelunker frame of exploring caves in a side-scrolling platformer fashion. For one, the player can choose between multiple characters to play as, each with varying stats and abilities, and equip them. The player character now has a health bar, rather than the "one hit kill" status of Spelunker's fragile protagonist.
Odder is the concept of "toku", or virtue. Performing heinous acts such as slaughtering innocent wildlife will, upon entering one of the holes of the game, send the player directly to the underworld to be judged by a demon for their actions. Players must ensure their actions are moral if they are to proceed with purloining artifacts from pre-industrial societies.
Spelunker II uses a 3/4 view that had recently been popularized by Konami's Ganbare Goemon, allowing the player to move left and right but also up and down at specifically marked locations to enter new areas. Players can attack with the default sword, a short-range weapon, or attack from a distance with a long-range weapon with limited ammo.
Players can also explore dungeons and caves, much like the original Spelunker, though these tend to be filled with tough enemies. Worse are the supernatural enemies like ghosts and zombies, which are immune to the player's default weapons until they can locate a crucifix item with which to combat them. Even so, the player needs high toku in order to use it.
The three heroes the player can choose from include: The Explorer, the default gun-toting character and one of the few carry-overs from the first Spelunker; the Esper, a psionics user that can fire lightning; and the Wizard, who sends out fireballs.