Memories With Oda-san

Memories With Oda-san: A Manga is a special one-shot written and drawn by Toriko creator Mitsutoshi Shimabukuro to commemorate One Piece's 20th anniversary. It was published in the Weekly Shonen Jump issue dedicated to the same, directly after Chapter 872.

Plot
Instead of a conventional plot, Shimabukuro (a self-described "Level 5 Manga Maker") compiles a mostly-chronological memoir of how Oda ("Level 99") has interacted with his life, and vice-versa: Shimabukuro concludes by recounting his favorite chapter of One Piece, and congratulates Oda on twenty years of success—with so many more to come.
 * 1993: Shimabukuro, still a high-schooler in Okinawa, encounters Oda's premiere work Wanted! in a compilation of Tezuka/Akatsuka winners. A manga aspirant himself, he immediately recognizes the quality of Oda's art.
 * 1994: While scouting for work with Jump in Tokyo, Shimabukuro re-encounters Oda's work in Ikki Yako and Monsters. He soon recognizes both—published under Oda's real name—as an evolution of Wanted! in style.
 * 1995: At a party for manga-industry rookies, Shimabukuro meets Oda in person for the first time. They become fast friends, sharing many drinks in-between assistant work and failed serialization attempts.
 * 1997: In May, Jump finally approves serialization for both Shimabukuro's Takeshi and Oda's One Piece. The pair exchange congratulations, and premiere in consecutive issues of Jump in July; each series tops the reader poll of its premiere issue.
 * 2002/3: Takeshi ends, but Oda gives Shimabukuro support and encouragement for his next series Ring. Subsequently, Shimabukuro requests his first and only autograph from Oda, as a gift for his hospitalized sister.
 * 2007/8: With One Piece ten years into publication, Shimabukuro premieres Toriko. Overwhelmed by the return to weekly deadlines, he commiserates with Oda, who cautions against hiring someone to manage his assistants, instead of interacting with them directly.
 * 2011: Shimabukuro and Oda collaborate on a crossover one-shot between Toriko and One Piece, with the former drafting most of the layouts and the latter completing most of the inking and fine-detail. Shimabukuro deems this the fondest of his memories.
 * 2016: KochiKame ends, leaving One Piece the oldest ongoing series in Jump. Not long after, Toriko ends, and Oda holds a commemorative party with Shimabukuro.

Trivia

 * While none of the facts given by Shimabukuro have been openly disputed, the one-shot does feature at least some artistic license.