@FlyingThunder the author has been heavily implying in this manga that intimacy happens outside of the drawn story, with a topping Takagi. What we see is just foreplay, and they keep it innocent because their kid is with them. Takagi pokes Nishikata because she knows she can, as he will always keep his composure if their daughter is there.
That's why the author never escalates, that's why you almost never see their bedroom. They still go to sleep at night in the same bedroom, and I'm pretty sure a whole day of teasing does have the obvious conclusion before going to sleep, but obviously, that happens outside what's drawn and it's up to us to connect the dots.
Plenty of real life couples do this when they have kids.