After the Sun Mutated, I Became a Modified Freak

(A story about humans all being transformed into monsters and fighting as modified beings, in the style of the Showa-era Kamen Riders. The protagonist isn't some lofty hero or a Rider, just an ordinary modified monster.)

One day, the sun underwent a mutation. It killed 90% of humanity, while the surviving 10% were reborn beneath the changed sun and gained superpowers.

Nan Gong Riyou was one of the survivors. He gained the power of the System, which lets him absorb the sun's energy and evolve. Now he and all of humanity must face the mutated creatures born beneath the sun, as well as impostors and objects that can disguise themselves as humans!

Humanity faces a world where fighting is the only way to survive! See how Nan Gong Riyou makes his mark on an Earth that has become a living hell!