Back before the two got together, Salem and Atlas were friends.
It was kind of unexpected, from all sides. They got strange looks for a while, when they would hang out at school. As mentioned several times, they were quite opposite: Salem being such a good kid, and Atlas bad. It was an unlikely duo.
Salem remembers the first time Atlas visited him at lunch. He was skipping class, so he didn't stick around—although even on the rare occasion they had a lunch period together, he still wouldn't sit with them the whole time. Atlas had wanted to discuss a video game that they were going to play together, and Salem had only mentioned him to his friends a handful of times. Zona was concerned, and a bit suspicious. Milo and Cam were visibly uncomfortable.