Well, that explains it.
Panel 1: Sigma’s apartment. A close-up of Xi lying on Sigma’s lap on the couch. She asks “Why did Rho decide to move out, anyway?”. Sigma replies (off-panel) “Uhm, well…”
Panel 2: A nervous Sigma, sweating, with a big thought bubble over him. Inside the thought bubble there’s a memory of Rho and Sigma. Rho’s holding his head with his hands with an excited smile, and says “What? You have a girlfriend? Oh man, okay—I’m moving out!!”. Sigma, with a desperate expression, says “WHAT?” in bold letters. Rho replies “You got this, bro!!”
Panel 3: Back to Sigma and Xi on the couch. Sigma says with a blank expression, “He said it’d be better for us to be more independent”. Xi closes her eyes and replies “Oh, that’s nice.”