An opposites attract series about adult couple Akari and Shiho. In chapter 17 they go on a date to an aquarium.
The concept for this series contrasts Akari's positivity with Shiho's low energy, so with Shiho it's intentionally hard to tell when she's happy, but even with Akari there's a brittleness to her cheerfulness. I don't know whether it's an intended effect, but I'm not sure they weren't underwhelmed by the aquarium.