It just means that he's more in-tune with her feelings than we thought.
However for his sake I hope she doesn't mention her harrowing past.
There's no telling what he might do.
Her not mentioning her traumatic encounter with the slimeball that I hereby dub Admiral Mizonezu (溝鼠, literally "Sewer Rat"; because when I looked at his face right now, that's what came to my mind on the spot) does not preclude Robba-san discovering it anyway in a much more horrible fashion: Turning around the corner as he's nearing the meeting spot for another date with Kashima, only to see her held captive a nearby alleyway by Mizonezu and a few thugs (whether they had encountered her by chance or had been stalking her for a while is equally possible), with her clothes already torn up / disheveled as Mizonezu takes his sweet time breaking her spirit.
Me, I dearly wish that either Robba-san or Kaga or both would manage to traumatize Mizonezu so hard that from then on he goes through a massive panic attack every time he sees anyone who even remotely reminds him of Kashima/Kaga/Robba-san.
... And I just realized that I keep referring to Robba-san as... well, Robba-san. It's like his name refuses to lose the honorific suffix in my mind; it just looks/sounds so wrong to call him just "Robba".