There's probably nothing going on behind her... There's nothing ominous back there. The comic will use a narration style with Ran's thoughts in the yellow boxes. The idea is the yellow feels like it's a post-it note and she's potentially detailing out things in her files as she's writing things down... hence the lowercase/ handwriting styled font for them.
Panel 1:
Ran (Narration) My name is Ran, Kimura Ran, and I'm a private investigator.
Ran (Narration): What exactly do I investigate?
Ran (Narration): Well, typically it's whatever pays the best.
Panel 2:
Ran (Narration): Getting proof of a cheating spouse. Tracking down a lost loved one. Finding evidence of fraud...
Ran (Narration): Every now and again I'll get a really interesting case--
Panel 3:
Ran (Narration): --Like this one.