I used to be a mailman, but then some faggot in a checker suit pissed me off and stole my cargo. And I ain't paying for the mail insurance!
Fallout is in some ways a bit like Touhou, beat up a couple of people or kill their "friends" and all of a sudden they become your companion later on down the road.
This could be taken as somewhat depressing, however. Consider, the line about calling the Courier 'Admiral' to 'maintain their mental balance.' Depending on what happened to cause two Japanese kanmusu to be on this side of the world, at least 150 miles from the nearest coast, in the middle of a desert. And they're calling this person who they tried to mug (and failed) 'Admiral' because otherwise they would break down mentally.
Par for the course in Fallout, but leads to some questions, doesn't it.
Nuka Cola is the best way to chill. Especially if it's cold
Afterword
The Mojave Wastelands of the United States of America.
Having attempted to attack a young courier to mug him, Tenryuu and Kiso had the tables turned on them instead. Afterward, they maintained their mental balance by calling this young man "Admiral" and tagging along with him.