Castlevania: The Arcade
The late-era Castlevania series has been marked by experimentation. While most of the series is marked by an emphasis on classic platforming and Metroidvania elements, the later games in the series have pushed away from that sweet spot for more experimental fare. Castlevania: Judgment was a console-based fighting game, Castlevania: Harmony of Despair tried its hand at multi-player Online game play, and the Lords of Shadow sub-series completely rebooted everything about the games for something more akin to God of War.
Even among these experiments, though, one title does stand out for how off the wall it is: Castlevania: The Arcade. While you could see the connective thread between all the previous games (this one has platforming, that one at least has characters you control in an arena), The Arcade was an on-rails light gun-based shooter (or, really, "whipper"). It's about as far as you can get from the main Castlevania series without being, say, Mahjong or Video Poker.
So what inspired Konami to release this title? Not only is it a weird entry for the series but it's an arcade game (as the title implies), and it's not as if the arcade market in the U.S. has been all that stable for the last couple of decades. Sure, arcades are still popular in Japan, but that's a tiny market for a large, expansive, Triple-A video game release. The fact that it never made it outside the Japanese shores (at least, not officially) speaks to the limited market for a game like this, even before we take into account how weird it is.
Sadly, details on the development and story behind Castlevania: The Arcade are scarce. This game came out at a time when the Castlevania series was in flux, with Konami having already shelved one reboot of the series (Castlevania 2008) and this title, along with the aforementioned Judgment and Harmony of Despair, illustrate Konami's desire to push the series outside its bounds and find new ways to grow a new fan-base for the series. It failed, and the game was quietly ushered away so that the company could reboot and then abandon the series to cellphones and gambling machines.
That leaves Castlevania: The Arcade as little more than a footnote to the series for most fans. Most of us will never get a chance to experience this game, due to how few machines were produced and the limited number imported to the West. The game is a curiosity, this weird thing Konami made once and then ignored, like so many other of their late-era projects with the series.