Second season of Gaikotsu Kishi-sama, Tadaima Isekai e Odekakechuu.

The Adrasia empire on the Vogel continent. There is a battle over the throne of such an empire that possesses powerful military and vast territory. With the successor undecided, the children of the emperor are vying to expand their power. However, there was one prince that everyone says will definitely not become the emperor: the seventh prince, Arnold Lakes Adler. The young man who was inferior to his younger twin brother in every way, the dull prince. Incompetent and lethargic, Arnold wastes everyday just playing around. However, behind the scenes, he is one of the only five SS-Class adventurers called Silver. Seeing the intensifying battle for the throne he decided I don't want to die, so let's have my little brother become the emperor... This is the tale of absurd secret maneuvers of the prince who is uninterested in the title of the emperor. (Source: Shousetsuka ni Narou, translated)

In an isolated village, two twins were born, separated by day and night. It is years later, and while the older brother Yuru has become a hunter of animals, his sister Asa has been locked away in a cage, ordered to perform a special duty that prohibits her from meeting more than a few select individuals. On an otherwise inconspicuous day, a group of armed men riding in helicopters, referred to as dragons by the citizens, assaults the village in search of Yuru, killing every adult on sight. When Yuru attempts to meet up with Asa and flee, he finds a dead body instead—on top of that, the person who killed her claims to be Yuru's true twin sister. Before the woman can capture him, Yuru is rescued by a man named Ryuu Dera Tadera, an outsider who frequently visits the village. However, it is not long before the two are cornered. In a last-ditch effort, Dera makes Yuru give a gift to the deity of the village, summoning a pair of daemons whose existence is bound to reveal the truth behind these chaotic events.

Barely surviving in a barrel after passing through a terrible whirlpool at sea, carefree Monkey D. Luffy ends up aboard a ship under attack by fearsome pirates. Despite being a naive-looking teenager, he is not to be underestimated. Unmatched in battle, Luffy is a pirate himself who resolutely pursues the coveted One Piece treasure and the King of the Pirates title that comes with it. The late King of the Pirates, Gol D. Roger, stirred up the world before his death by disclosing the whereabouts of his hoard of riches and daring everyone to obtain it. Ever since then, countless powerful pirates have sailed dangerous seas for the prized One Piece only to never return. Although Luffy lacks a crew and a proper ship, he is endowed with a superhuman ability and an unbreakable spirit that make him not only a formidable adversary but also an inspiration to many. As he faces numerous challenges with a big smile on his face, Luffy gathers one-of-a-kind companions to join him in his ambitious endeavor, together embracing perils and wonders on their once-in-a-lifetime adventure.