Figure | JoJo's Bizarre Adventure: Phantom Blood | Jonathan Joestar

Jonathan Joestar is the protagonist of Phantom Blood and the first JoJo of the JoJo’s Bizarre adventure series. He is an honest and kind man, but his life would  be changed after meeting his adopted older brother Dio Brando. Jonathan would become a Ripple user with the guidance of his master Will Anthonio Zeppeli.

JoJo's Bizarre Adventure: Phantom Blood
The story follows Jonathan Joestar as he matures with and eventually combats his adoptive brother, the cunning and merciless Dio Brando.

As part of his scheme, Dio torments Jonathan in ways such as violently beating him in a boxing match and turning his friends against him, all while presenting himself before Jonathan's father as a better gentleman and student than his adoptive brother. When Jonathan finds solace in a relationship with his girlfriend Erina Pendleton, Dio steals her first kiss.

Dio eventually becomes a vampire, leading to Jonathan fighting him for humanity's sake.

(from Fandom JoJo's Bizarre Adventure Wiki)

JoJo's Bizarre Adventure (ジョジョの奇妙な冒険, JoJo no Kimyō na Bōken), often shortened to JoJo or abbreviated as JJBA, is a shonen and seinen manga written and illustrated by Hirohiko Araki. JoJo's genre spans Action, Adventure, Supernatural, Thriller, Comedy, Tragedy, Mystery, Slice of Life, and Horror. (from JoJo's Bizarre Encyclopedia)

The nickname "JoJo" is an abbreviation of the name of the Joestar family protagonists (Jonathan, Joseph, Jotaro, Josuke, Jolyne, Johnny, Jodio) in each of the eight manga story arcs whose adventures it chronicles.