Strongest Dichotomy

Mentioned Characters: Kasen
Story
What if there was a world where the hermit took her long-lost oni half's hand and swore to live alongside her again? Essentially, they are the same person, but they mix as well as oil and water. This is the tale of such a possibility. It's a tale that may or may not be true...

With a shout, Kasen slammed her fist into the enemy before her. The impact echoed like a peal of thunder, leaving nothing behind except for the certainty of her triumph and a sharp pain in her hand. Kasen has honed her senses to be aware of everything around her, but this small victory caused her to relax for the briefest moment... By the time she noticed the bullets coming at her from her narrow blind spot, it was too late to dodge. Kasen braced herself for the pain... that never arrived. She had forgotten that she was no longer fighting alone. "A little overconfident, aren't we? Shouldn't you be focusing more on the battle?" "...I had it under control." "Sure. Keep telling yourself that." The girl who spoke was her mirror image in almost every aspect except for the two horns protruding from her head, which resembled sharpened stakes of gnarled wood. Her precious right arm stood beside her.

"Too easy." The oni clenched her fist, savoring the thrill of combat. Until now, she believed that all the mock "battles" conducted here were beneath her, considering how she had overcome battles to the death, wars, and countless other hardships. As an oni, she enjoyed nothing more than showcasing her strength by defeating strong opponents, but she hardly needed to exert herself to crush the weaklings surrounding her. That said, tossing them aside one after the other did feel kind of nice. Glancing beside her, she noticed her other half was on the defensive. "What is she doing?" she thought to herself. "Stop making me look weak. Hmmm, it's kinda annoying seeing myself get hurt. Heh, I guess I'll help her out." She deflected the bullets pelting toward Kasen with a sweep of her hand. As Kasen's right arm, she was committed to supporting her as best she could.

Like a hurricane, they lashed out with a flurry of explosive kicks at the puppets surrounding them. Each one they struck could do nothing but wail like a beast as its body, paralyzed with pain, plummeted to the ground. But no matter how many they defeated, there were always more blood-crazed puppets to replace them. A crack appeared in the sky, indicating that the Senkai couldn't last much longer. The end was fast approaching, and there was only one way for them to possibly stop it... "This is pretty fun, huh?" "Focus!" Back to back, they unconsciously synchronized their breathing. Together, they could brave the fires of Hell and soar to heights unknown.

The oni and the hermit were a frenzy of motion as they unleashed blow after blow. They were so perfectly in synch that they looked like a reflection of each other. The good and evil that had long been separated came together once more. They fought as one, but it was also like a single entity was acting through them both. "Wrooooah!" Their thunderous roar shook all who heard it. The oni and the hermit were walking down the same path, and those in their way had two choices: either step aside or fall before them. What happened next? What happened when the two finally became one? This is merely the first chapter of a tale that may or may not be true...