Kana's probably my favorite girl in the game, but I felt like her path was completely derailed after the absolutely terrible sex scene in Part 5.
I get this, and I felt similar narrative whiplash at the sudden "dtf?" by Kana from out of nowhere. The scene itself wasn't as bad as you indicate though, at least IMO, because the way Kana treated it like a competition – where she had to face defeat in the face of the MC's stamina – made it very interesting and memorable to me. As you say though, it was the well-written scene the next morning that allowed things to flow much better once Chapter 6 played out. We still don't know Kana's motivations any better, but we do understand the relationship they are forming more clearly.
I still wonder if the sudden sex scene came down to an overall pacing issue, in that while buildup and anticipation is essential in adding eroticism to an interaction, there's a fine line between that and feeling cock-blocked, or just plain losing interest. And many games fail at finding a good balance in that area. Perhaps with Kana being sidelined in Chapter 6 the dev realized that something significant needed to happen in Chapter 5 to hold the interest of her fans?
The usual way that would be done is with a heavy petting or handjob/light blowjob scene that could feel somewhat non-committal, while still giving the promise of more in the future. But to me, that doesn't really feel like Kana. She's going to give it her all once she decides she wants something, so I can understand why the dev might choose to make it an all-night no-holes-barred affair once she made up her mind.
As a result, it's a lot easier to sit back and enjoy the character moments – and there are plenty of those. Elspeth's fear of flying seems a bit arbitrary, but it does make for a nice bonding opportunity.
I found it arbitrary too at first, considering how she has so little hesitancy in anything else she does, and how strong she appears when facing challenges that would deter most. I realized though that her personality is very focused on being in control, and so it makes a lot of sense that she would not like experiencing the loss of control when putting your life in the hands of an unknown pilot. All her data gathering, uncovering secrets, letting people hear what they want to hear by speaking in half-truths...it's all meant to keep her in control of every possible situation. That's how she feels comfortable.
Her cattiness towards the other girls is probably her least attractive feature (in my eyes, anyway), but it very much fits her character and so far she knows how to walk the line between being protective and insufferable.
Elspeth is...human. I'm not as blind to her issues as I was upon my first read (thanks to minor things others have pointed out about her actions), but I'm pretty sure she isn't a full-blown monster like some perceive her to be. As I have argued before, if she really wanted to destroy the other girls and win the MC's heart, then there are a whole lot of cruel ways an intelligent woman like her could do that. The fact that she doesn't, and instead even encourages them to try their best (as in her heart-to-heart with Vi), tells me otherwise.
Viridiana, meanwhile, feels too much like a sister for me to be interested in her sexually (ironic around here, I realize).
Ironic? That's a strange way to spell "blasphemy" on F95.
I agree with you though, FWIW. In some ways, I actually find Amrit to be more sisterly than Vi, and have to leave her by her lonesome as well because of that (though I'll be more than happy to see Amrit end up with Kana on my Elspeth-exclusive playthrough if that path is offered). That is, unless the dev chooses to give us an Elspeth-Kana option. Not as a permanent thing mind you, but honestly Kana is the only one I can see Elspeth considering for a fun and special 3-some with the MC, since all the other LI's are so close to her and feel like her younger sisters. Plus, the way Els ogled Kana when first meeting her has my mind doing all sorts of strange rationalizations for this unlikely pairing.
Hey, a man can dream, right?