The name Tarou Sakamoto once instilled fear in every villain. No other professional hitman matched his prowess, and fellow assassins revered him. However, Sakamoto fell in love. In five short years, he married, became a father, put on some weight, and traded his weapons for an apron as he became the owner of a humble convenience store. Although Sakamoto is decidedly retired, he finds his old life of crime hard to shake off. His former partner, Shin Asakura, reappears and resolves to stay with Sakamoto's family under their strict no-kill rule. To make matters worse, a large bounty is placed on Sakamoto's head. Numerous assassins now pursue him—but they are in for a surprise. Sakamoto has not lost his edge, and no matter what tricks his enemies pull, he will fight off every last one to protect his dear family.

High school student Wakana Gojou spends his days perfecting the art of making hina dolls, hoping to eventually reach his grandfather's level of expertise. While his fellow teenagers busy themselves with pop culture, Gojou finds bliss in sewing clothes for his dolls. Nonetheless, he goes to great lengths to keep his unique hobby a secret, as he believes that he would be ridiculed were it revealed. Enter Marin Kitagawa, an extraordinarily pretty girl whose confidence and poise are in stark contrast to Gojou's meekness. It would defy common sense for the friendless Gojou to mix with the likes of Kitagawa, who is always surrounded by her peers. However, the unimaginable happens when Kitagawa discovers Gojou's prowess with a sewing machine and brightly confesses to him about her own hobby: cosplay. Because her sewing skills are pitiable, she decides to enlist his help. As Gojou and Kitagawa work together on one cosplay outfit after another, they cannot help but grow close—even though their lives are worlds apart.

Iori Kitahara moves to the coastal town of Izu for his freshman year at its university, taking residence above Grand Blue, his uncle's scuba diving shop. Iori has high hopes and dreams about having the ideal college experience, but when he enters the shop he is sucked into the alcoholic activities of the carefree members of the Diving Club who frequent the place. Persuaded by upperclassmen Shinji Tokita and Ryuujirou Kotobuki, Iori reluctantly joins their bizarre party. His cousin Chisa Kotegawa later walks in and catches him in the act, earning Iori her utter disdain. Based on Kenji Inoue and Kimitake Yoshioka's popular comedy manga, Grand Blue follows Iori's misadventures with his eccentric new friends as he strives to realize his ideal college dream, while also learning how to scuba dive.

Life in the bustling city of Orario is never dull, especially for Bell Cranel, a naïve young man who hopes to become the greatest adventurer in the land. After a chance encounter with the lonely goddess, Hestia, his dreams become a little closer to reality. With her support, Bell embarks on a fantastic quest as he ventures deep within the city's monster-filled catacombs, known only as the Dungeon. Death lurks around every corner in the cavernous depths of this terrifying labyrinth, and a mysterious power moves amidst the shadows. Even on the surface, survival is a hard-earned privilege. Indeed, nothing is ever certain in a world where gods and humans live and work together, especially when they often struggle to get along. One thing is for sure, though: a myriad of blunders, triumphs and friendships awaits the dauntlessly optimistic protagonist of this herculean tale.