Monsters

Monsters (モンスター) is a oneshot manga by Eiichiro Oda.

Plot
In this manga, Ryuuma (who resembles Roronoa Zoro) had traveled to a town. Ryuuma unfortunately had at the time no money to pay for food. He had gone for five days without food and his starvation was starting to get to him. Luckily he was saved by a kind waitress of the Restaurant Gèrard, Flare. For giving him food, Ryuuma decided to repay his debt to the red haired girl. Unfortunately for him, she was at the time talking to a swordsman, Shirano (who looks like Mihawk), and thus ignored him. Just as Shirano was leaving, his sword sheath accidentally touched Ryuuma's. Ryuuma took this as sign for a duel to the death and decided to fight Shirano. As the two swordsmen engaged each other, Ryuuma slashed a copper Buddha easily in half. Just before the fight could escalate, Flare asked Ryuuma to stop. This he did much to shock to everyone in the restaurant.

Later, Ryuuma learned from the restaurant's owner of the story of Flare's hometown that happened seven years ago. Ryuuma learned that the town was attacked by a dragon and the only survivors were Flare and Shirano. Later after eating, Ryuuma decided to continue traveling. As he was walking, Ryuuma's sheath was touched by another. Instinctively, Ryuuma thought of it as a challenge. However before he could do anything, the swordsman, D.R., was apparently stabbed. D.R., seeing that he was stabbed, decided to blow the Dragon Horn he allegedly stole and supposedly summoned a dragon to come to the area. He did so in order take the whole town with him. He then broke the horn so no one could stop the dragon and then apparently died. This caused an uproar in the town and Ryuuma was blamed for it. And he was mad about that.

Ryuuma, not understanding the situation at all, decided not to take responsibility despite the townspeople and Flare's anger towards him. Shirano however confirmed that the horn was real and asked everyone to leave so that he can deal with the dragon. Flare, feeling bad, decided not to go. Ryuuma, being in debt, decided not to leave as well. Flare, fearing that Shirano might die, decided to stop him. Ryuuma decided to follow her and try to stop her. However just as they got to a certain location, Ryuuma tried to stop Flare from looking in a certain direction. He unfortunately failed and she saw that Shirano was helping D.R. loot the town. It turned out that Shirano and D.R. were partners from the start. Shirano had told D.R. of thing with Ryuuma's sheath so that they could stage a scene with a fake Dragon Horn. They did so in order to scare everyone so they could steal from the town. It was then revealed that they too were responsible for the attack that happened seven years ago.

D.R. had summoned a dragon with a Dragon Horn that Shirano stole from his own subordinates to attack Flare's hometown. While in the chaos, Shirano found Flare and killed her father while she was unconscious. Shirano then decided to use Flare in order to gain some prestige for his name. Learning of this new info, Ryuuma told Flare to leave as a dragon was still coming to destroy the town. She however didn't and cried. Ryuuma then decided to confront Shirano and D.R. Upon meeting up with Shirano with D.R., Shirano merely mocked Ryuuma and attacked him. Ryuuma however dodged Shirano's attack and killed him with one stroke. D.R. frightened by this, pleaded for his life by saying that only he could stop the dragon from coming with the real Dragon Horn. Ryuuma however instead slew the villain.

Just as the dragon arrived, Ryuuma leaped from a building and with one mighty swing, slew the beast. Afterward, Ryuuma decided to leave town. As went, he left Flare with some encouraging words and told her that she owed him one as he fought for her twice. Later when the townspeople came back and discovered everything, it was learned that Ryuuma was called "The King". It was a name that was given to him by people he had saved. Ryuuma despite his fame, however doesn't know this himself and even plans to fight this "King" one day. Ryuuma, despite it all, however simply travels off to his next adventure.

Trivia

 * In Oda's current manga One Piece, there is a character referring to Ryuuma. Samurai Ryuuma, a zombie created by Dr. Hogback and Gecko Moria, was brought to life with Brook's shadow. He is said to hail from Wano Country (a parody of "Wa no Kuni" or "Japan"), and was said to have slain a dragon just like this story's Ryuuma. According to Oda, both Ryuuma are the same character, thus this makes Monsters the only previous story of Oda's (other than Romance Dawn) to actually be a part of One Piece's universe, at least for now.
 * D.R., one of the antagonists in the Monsters story, has a wanted poster that can be seen in episode 45 of the anime on the wall on Fullbody's ship. Another poster can be seen in episode 48 when Luffy goes to the Gold Roger Bar.