Here are some MHA-style names reflecting the Yin and Yang duality, incorporating light and darkness powers:

Hero Names:

• Luminaris Umbra: Combines "Luminaris" (light) and "Umbra" (shadow), suggesting a balance between the two forces.
• Solarian Nox: "Solarian" evokes the sun and light, while "Nox" represents night and darkness.
• Shiro Kuro: Simple yet effective, using Japanese words for "white" (Shiro) and "black" (Kuro).
• Daybreak Eclipse: A dramatic name highlighting the contrast between the beginning of light and the obscuring of it.
• Zenith Nadir: Astronomical terms representing the highest and lowest points, symbolizing the extremes of light and darkness.
• Aether Tenebris: "Aether" suggests a bright, ethereal quality, while "Tenebris" means darkness.
• Lux Tenebrae: Latin for "Light Darkness," a straightforward and powerful name.

Villain Names:

• Obsidian Sol: A paradoxical name, combining the dark, volcanic Obsidian with the bright Sol (sun).
• Nightshade Aurora: "Nightshade" is a poisonous plant, representing darkness, while "Aurora" is a beautiful light display.
• Shadowflare: A name that suggests a sudden burst of darkness.
• Voidbringer: A name that suggests the power to bring about darkness and emptiness.
• Umbralis Rex: "Umbralis" (shadowy) combined with "Rex" (king), suggesting a ruler of darkness.
• Blacksun: A simple, yet impactful name that directly contrasts light and darkness.
• Eclipsebringer: Suggests the power to cause an eclipse, blocking out the light.

Names that could work for either hero or villain, depending on context:

• Dualitas: Latin for "duality," reflecting the user's ability to switch between powers.
• Equilibrio: Latin for "balance," suggesting a mastery of both light and dark.
• Polaris: The North Star, representing a point of balance between opposing forces.
• Chrysalis: The transformative stage between larva and butterfly, symbolizing the shift between light and dark powers.

These names offer a variety of styles and tones, allowing for flexibility in character development. Remember to consider the overall personality and backstory of your character when making your final selection.