It turns out that this game is very unique, in that the single-player mode has RPG mechanics. You choose which opponent to fight, and can see their 5 stats before the fight, as well as your own character's stats. If you win, you gain stat improvements *relative* to the difference between your opponents stats and your own. For example, if your opponent has much higher STR than you, you will gain a bunch of STR by defeating them. Thus, you can slowly level up by fighting the same opponents over and over again, and decide when you are strong enough to fight the next guy. This is a brilliant idea for a single-player mode in a fighting game.
Inspired by Giant Bomb playing this in the 'Ranking of Fighters' series, I tried playing the single player mode of this game.
completed the game on 3 difficulty.
After a bunch of grinding against WARREN, I was strong enough to start fighting my way up the ranks and finally beat RANKER, the final boss.