Spin-off that takes place 8 years after the events in Full Ahead! Coco.

The Gekido is a giant steam pillar that divides the ocean into two regions. Eight years ago, the darkness that consumes the other side leaked into this side leaving the ocean pitch black. The only people that go out to sea now are fools and pirates. A young man named Cherry Blossom has a dream to travel the ocean and goes on a journey with a boy named Son who somehow is in possession of the Teardrop of the Gekido, a mysterious item which is said to hold the key for traveling the dark sea.

(Source: MangaHelpers)

Goemon Ishikawa, the legendary king of thieves from the feudal era, has come to know that there is an important treasure being transported from the Imperial Palace to the Kamiyama mansion; an ancient artifact called "moon's melody box" (月詠みの箱). Surprised by the extreme measures taken by the guards of this treasure, his indomitable spirit aches to steal this rare item that once a year can grant one special wish to whoever possesses the box, but it will not be so easy to steal it. Even worse, once it is opened, it will be harder to deal with the unusual contents of the box.
(Source: Wikipedia)

This is the story of Coco, an orphan kid who wanted to be a pirate, and his role model, "Crazy" Barts, a pirate without a port who is feared by the peasants but despised by the other pirates.

Himawari Sakura's father has passed away and she has inherited all of the yakuza organization. To protect her, Iwama Chibaki (a man with a distorted past) gets hired.
(Source: MU)