Kaguya-sama: Dropping keigo when narrating?

Question

Related: Kaguya-sama: 女の子 (onnanoko) as an opposite for 男子 (danshi)?

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In Kaguya-sama Chapter 52 / S02E02, there's a character named Moeha Fujiwara (the imouto of a main character Chika Fujiwara) who talks about Kei Shirogane (the imouto of the male protagonist Miyuki Shirogane) to Kaguya Shinomiya (the female protagonist and title character) as follows:

圭ちゃんかわいいよね？

ウチのクラスの男子は勿論だけど

女の子からもすっごくモテるんだよ。

In manga:

In anime:

See 0:11 - 0:18 here.

Question 1: I could be missing something, but does Moeha actually NOT use keigo with Kaguya when talking about Kei and then later when talking directly to Kaguya uses keigo?

• Later in the manga:

Question 2: If so, then what's up with this: Do you like not really use keigo or something when 'narrating' or describing someone else to someone you'd normally use keigo with? (Well if not, then maybe it's a hint? Lol.) If not, then, what, Moeha is indeed using keigo throughout?

• Note 1: Not sure if relevant, but Yuta says 3:34 here: In that school everybody pretty much uses keigo with everybody else.

• Note 2: In S03E10, Kaguya and Moeha meet again, and they use keigo with each other. Actually here's the full compilation:

Afaik, Moeha Fujiwara and Kaguya Shinomiya have interacted on-screen only in S02E02 and S03E10. Their conversations are broken down into:

1. S02E02 at the start of their outing with Chika and Kei Shirogane when Moeha talks about Kei to Kaguya (Moeha: Kei is cute, and I want to lock up Kei in a dungeon.) - Not keigo. - See 0:11 to 0:25 here.

2. S02E02 briefly right after (1) above when Moeha talks (about Kaguya) to Kaguya. (Moeha: You're at the top of my list of things I love to the point that I'd want to eat you.) - Keigo. - See 0:32 to 0:40 here. (I guess 0:25-0:32 isn't keigo, but I guess I won't count it for the same reason as (3) below.)

3. S02E02 at the end of their outing when Moeha invites Kaguya for a group hug - Either not keigo or N/A since just 1 line. - See 1:25 to 1:30 here.

4. S03E10 when Moeha talks about Miyuki to Kaguya - Keigo. - See 2:20 to 3:01 here.

5. Summary: The only time Moeha doesn't talk keigo to Kaguya is when Moeha is talking about Kei.

Answer 1

In a relationship like these two, whether to use keigo or not depends on the mood, the atmosphere, the people around them, and all other circumstances. Grammar has little to do with it. In the first scene, she may have been a bit more excited than usual because she was talking about her close friend. In the second scene, the author may have thought this scene would look scarier if she used keigo (because it implies she was serious).

I don't know why you are concerned about "narrating", but it has nothing to do with it.

Answer 2

Moving between keigo and keigo-free can mean the speaker is testing a boundary - whether the other is willing to be talking more casually. When the other doesn't reciprocate, the speaker might fallback to keigo. The difference between -だよ and -ですよ is not a too drastic one, and it could mean nothing, though.