Each girl's bond story UI is visually themed after hearts, with the line of Shared Moments taking the shape of an electrocardiograph. The number of Moments at the start is sparse, but as your affection level with the girl grows, so does the frequency of Shared Moments until they're covering up the empty space by the end—just like the common romance of a heartbeat growing quicker near the one you like.
The Difficulty Spike that happens for every Campaign chapter can be justified according to the circumstances, especially for the ones before and after Chapter 13—chapters before 13 mainly take place on Princess Island, your home turf, and even on operations outside of the Island, you're always supported by R.o.S.E.; after Chapter 13, you're thrust into completely unknown territory, cut off from R.o.S.E., working with limited resources and the Allied Army's lackluster technology.
The Fantasy Oath screen has you interact with constellations spangling in the night sky, each representing a girl's Oath. With the knowledge that these are actually simulated dreams of what you and the girls wish for, this makes it a Visual Pun of wishing on a star.
When selecting waitresses for the Café, the addition of the four newest girls—Shirou, Aniya, Kaanal, and Yui—allows you to substitute each one for another of the original squad because of a Commonality Connection.
Yuki and Yui are the most obvious: they aren't just twins, they're clones of the same batch with even some of the same like and dislikes. Yui can even act like Yuki perfectly, enough to fool Lida and Moon when they unknowingly first meet her.
Cornelia and Shirou are the most involved of the girls in military matters... even if the difference in experience between the veteran and the untested respectively is like an elephant looming over an ant. This seems to be also why Shirou respects Cornelia a lot.
Eksistere and Aniya have scientific origins involving the Allied Army, the former being an Ionus test subject of the Structural Research Institute, being a group under the Allied Army, and Aniya an android creation of the Army.
Lida and Kaanal both might seem like your average youngster, but they have Deliberate Values Dissonance—Lida because she lived a life on the streets right after the Outbreak doing whatever it took to survive and learnt nothing about basic morality or luxuries, Kaanal because she's actually an Alpha learning about human society.
