I like his casual "You're paying for that door repair", he was probably waiting to see how long it took for her to notice. Also @Just_a_Simple_Merchant called it back at comment #2090072.
I hope Guin starts to explain this Doctor's past, otherwise the plot around this strip is going to feel pointless.
TLDR: Doc fell in love with a Assassin of the Order and according to the Guin-verse, a certain Kancolle Doggo is apparently capable of seeing certain things...