The entire premise of this manga is that Kuru was a kuudere who defrosted into pure deredere. Part of that process is find points of commonality and slowly turning that into affection (e.g. Susumu's sister and Kuru liking the same capsule gacha). She also wasn't interested in the manga - you can tell that just from the dark shadow on her face and the sweat drop on Hina's face. She wanted to a bit of revenge for him seeing her panties earlier, but it didn't stick. Further, even in the 1960s and 1970s, adult men hid their porn from their wives and girlfriends just because it's awkward, so how does that make him a loser?
Anyway, if it's like the preserialization, Haru was born right after uni, and the second child will be conceived soon. The lingerie is to help counter those declining birh rates!