About Monkey D. Garp
Monkey D. Garp, also known as "Garp the Fist", is an extremely famous and powerful Marine Vice Admiral. He is the father of Monkey D. Dragon, the paternal grandfather of Monkey D. Luffy, and the adoptive grandfather of Portgas D. Ace. He was responsible for overseeing Ace's birth and raising a young Luffy, before entrusting them both to the Dadan Family.
A contemporary of Gol D. Roger in his prime, Garp came to be known as the only Marine that could seriously challenge the Pirate King, with feats to match; his participation in the God Valley Incident, that led to the defeat and disbanding of the infamous Rocks Pirates, won him the title "Hero of the Marines". At the same time, he has mentored many younger Marines into prominence, including once-Admiral Kuzan and SWORD members Koby and Helmeppo. After Ace's death at the Summit War of Marineford, Garp became an instructor to focus on training new recruits; while the public believes him to be retired, he still retains the rank of Vice Admiral.
During his mission to rescue Koby from the Blackbeard Pirates, Garp was badly injured and imprisoned on Hachinosu, being officially declared "missing in action" by the Marines.
Garp was first introduced during the Diary of Koby-Meppo cover arc, where he first took charge of training Koby and Helmeppo. Due to his actions, he is the main antagonist of the Post-Enies Lobby Arc and a supporting antagonist in the Marineford Arc.