(No System + Not Joining the Main Character’s Crew + Invincible in the Later Story)
In the year 1475 of the Sea Circle Calendar, Yige arrived in the world of pirates.
Other people either transmigrated as one of the Four Emperors or an admiral, or came equipped with a literal cheat.
But he was born as a baby of the Lunarian race, with no System and no golden finger.
Fortunately, he met Kozuki Toki, a Devil Fruit User, and made it through several crises!
He’s the lucky guy who escaped Mary Geoise with his hands clean, the savior of powerful characters doomed by the plot, the man who took away the whetstones along Luffy’s path to greatness...
Yige declares: Those who defy me will die! Those who obey me... will die too!
Let the sorrowful be engulfed in flames. The fallen cannot be forgiven. Wings that burn eternally, carry me away from the mire of the mortal world.
The pace is slow at first. Around 120 chapters in, the story reaches the point when Luffy sets sail.
You should give the protagonist a Devil Fruit so he can develop his career on Skypiea. Then, give the protagonist and his brother two more Devil Fruits: a Paramecia-type Gravity-Gravity Fruit and a Logia-type Rumble-Rumble Fruit. Ideally, also give them a Lunarian Devil Fruit and a Mythical Zoan-type Devil Fruit.
Why hasn't he eaten a Devil Fruit yet?
The author could consider strengthening the protagonist's mother's combat abilities.