The System Is the Strongest, but Only My Sister Is My Opponent

(There is a system, but it will not change time, and it will not transform into a Kamen Rider and travel through time. There is only one world view) (The heroine is to be determined) Traveling to the neon parallel world, Takahashi Yuuto awakened the [Kamen Rider System]. He can transform, he can fight, he can fly and kick - in theory, he can do anything. But in fact, there are no weirdos, monsters, or cosmic beings in this world. So for sixteen years, the only function of his system was: Go to Comic Con on the weekend, transform into Kamen Rider, stand under the spotlight and do some cool poses, and then listen to the beautiful ladies around you scream—— "Wow! So handsome!" "This armor is so cool!" "Please take a photo! Please take a photo!" Yuuto would smile and say "thank you" every time, then release the transformation with satisfaction and go home to continue being his ordinary high school student. Until one day, his sister Mio began to grow scales and claws.