JeanMarco

"'I just don't want those charred bones I saw to be disappointed in me. I...I know what I have to do now.'""—Jean after Marco's death"

JeanMarco is the slash ship between Jean Kirstein and Marco Bott from the Attack on Titan fandom.

Before Marco Died
Jean and Marco are canonically best friends and first met in the Training Camps since they were both 104th Training Corps Cadets. They are rarely seen without the other unless in battle. Their personalities are the total opposite of one another: Jean - is selfish, proud, bold, and realistic, in contrast to Marco who is kind-hearted, soft, and idealistic. Jean also has a strong sense of responsibility and Marco notices his qualities of a leader before anyone else, including Jean, does.

Marco is one of the few who believed in Jean's leadership skills in the beginning and trusted him when they were in trouble during the Battle of Trost District. Marco was also the one to comfort Jean when the latter felt insecure about his decisions during the battle as many were soldiers were lost.

Marco is the one to restrain Jean when he gets angry at some of Garrison's men, who left them for dead in the Battle of Trost District.

After His Death
When Marco dies in Primal Desire: The Struggle for Trost, Jean is the one to find his body. The shock from seeing Marco dead with only half his body left caused Jean to enter a semi-catatonic state. Marco's death leaves a deep impact on Jean as he chooses to join the Scout Regiment instead of the Military Police Brigade to honor Marco's death. Jean kisses his sword before fighting the Female Titan, perhaps to remember why/who he's fighting for. His sword hand is the same one he held Marco's ashes in.

Fanon
In the fandom, Jean is often portrayed as a "tsundere" and Marco's kindness and endless patience makes them get along well. Despite the ship name, Marco is usually the dominant one in the relationship in fanfictions/fanart.

Since Marco is dead in the canonverse, nearly all fanfictions/art takes place in an AU or before Marco's death. Popular AU's are College or high school AU's, Dark!Marco, and HomoMarco but NoHomoJean(where Jean is living in denial and falls for a very gay Marco).

Marco is sometimes called "Freckled Jesus" possibly referring to his signature freckles and him being a kind-hearted cinnamon roll to Jean.

Quotes
"'Your skill at recognizing a situation as it unfolds, gives you a clear grasp of what needs to be done now, you know? You made the right call. It's what got me moving. It's why I'm alive now.'""—Marco credits Jean for saving him"

Fandom
FANFICTION 

Marco Bott/Jean Kirstein tag on AO3

TUMBLR 

JeanMarco tag on Tumblr

Trivia

 * JeanMarco appears to be quite popular on AO3 with over 6000 fics.