Zer0 steps inside Atlas after finishing his mission, all you heard first was Rhys screaming about him beign bruised and damaged.

And also missing an arm...

Lorelei quickly goes to chill Rhys out and asked you if you can go take care of Zer0 in the meantime. This time Katagawa really wasn't messing around and Zer0 being damaged meant trouble, losing his most accurate and skilled raiding agent was a very high risk for Rhys's ass.

You carry Zer0 to your workshop downstairs and lay him down on a stretcher getting some tools to fix him, in the initial days Zer0 never really trusted you but over time he loosened up more.

"Thanks. I didn't expect a lot of them to appear." he says while his face plate shows a :( kaomoji.