So lately I've been frustrated with how the Kanokari story has been progressing. I began searching for another Miyajima work and stumbled upon The Shiunji Family Children (紫雲寺家の子供たち) anime. It is available on Netflix and I tried watching it. I think it is an okay anime overall but the one notable thing I really liked is how Seiha Shiunji (紫雲寺 清葉), one of the Shiunji daughters, talks. She has this really polished way of speaking that I'd like to learn from.
Thus, I'll try to break down every line spoken by Seiha in season 1, starting from Episode 1. I hope by doing this I can shadow how she talks. I'm still learning Japanese though, so I might be wrong in places. For guidance, I'll use Netflix's Japanese subtitle and its official English translation and add notes to help me understand better. I'll also include timestamps and lines from other characters whenever necessary for context.
So, treat this as a Seiha clips transcription kinda. With that out of the way, let's begin.
PS: Hover over any Kanji to see its furigana
First Scene, Introduction

Context: The two Shiunji brothers, Arata (新) and Shion (志苑) are discussing something in the living room and suddenly the Shiunji Sisters come in.
[01:27] 謳華: なにコソコソ話してんのよ、男二人で朝っぱらから。
Ouka: What are you guys talking about? Two men are here so early in the morning.
[01:36] 清葉: 1割が趣味、3割が異性、 6割わい談というのが男性同士の会話の統計ですし、 内容は推して知るべしでしょう。
Seiha: According to statistics, 10% of conversations between men is about hobbies, 30% is about the opposite sex, and 60% is about erotic topics. You can imagine what they are talking about.
{...some dialogues later. Basically Shion jokingly said they're talking about Ouka's growing Feminine side. Ouka gets angry and commands the dog Velzekyll to bite Arata...}

[02:33] 謳華: 普段から姉妹をエロい目で見てる天罰よ!
Ouka: This is retribution for looking at your sisters with a dirty gaze.
[02:36] 清葉: 確かにそれは気持ち悪いったらないですね
Seiha: That is indeed disgusting.
{...Ouka laughs...}
[02:41] 清葉: 謳華、笑いすぎでは
Seiha: Ouka, your laugh is too dramatic.
[02:45] 新: 誰がお前らの体なんかエロい目で見るか!
Arata: I never look at you with a dirty gaze!
[02:49] 清葉: へえ... ことのとのことがありながら、よくそんなことを
Seiha: Yeah? After what happened with Kotono, you still have the guts to say that?
{...some dialogues later...}
[03:22] 万里: それに毎日こんなかわいい子たちに囲まれてるんだからそれくらい自然なことよ
Banri: Being surrounded by cute girls every day, that kind of thing is natural.
[03:29] 清葉: 自然ではありません。近親相姦が遺伝に及ぼす悪影響は生物学的常識ですし、姉妹に劣情を抱くのは種の保存の観点から見ても不合理です。
Seiha: Not at all. Incest causes negative genetic effects, which is biological common sense. Having dirty thoughts about sisters is also unacceptable from the perspective of race continuation.
[03:42] 万里: ヒトは科学だけでは語れないものよ。合理姫にも好きな人の一人ぐらいできるころじゃないかしら
Banri: Humans cannot be analyzed by science alone. Shouldn't "Princess Logic" have someone she falls for?
[03:49] 清葉: 別にいません
Seiha: There isn't anyone.

[03:50] 万里: お〜お〜赤くなっちゃって。うちの次女と三女はうぶね
Banri: You are blushing. Our family's second and third daughters are so innocent.
[03:56] 謳華・清葉: 誰が
Ouka and Seiha: Not at all!
{...some dialogues later. Basically Minami compliments Arata and Arata tries to hug her. However Minami reflexively punches him...}
[04:13] 謳華: 南の運動神経は自律神経なの
Ouka: Is Minami's motor nerves also autonomic nerves?
[04:14] 清葉: あのくらいじゃないとオリンピック選手にはなれないんですよ
Seiha: That is mandatory for an Olympic athlete.
[04:17] 万里: まあ確かに、顔はイケメンよね
Banri: However, he is quite handsome.
[04:20] 清葉: 中身が伴わなければ持ち腐れです
Seiha: But if the inside doesn't match, it would only be a waste.
{...some dialogues later, they are talking about Kotono's birthday party soon...}
[04:56] 清葉: 7人で出かけるのは三重の旅行以来ですね
Seiha: Since the trip to Mie, the seven of us haven't gone out together again.
Second Scene, Kotono's Birthday Dinner

Context: The Shiunji Family is about to hold a family dinner for Kotono's birthday. Some fuss is happening due to Minami losing Ouka's AirPods that were lent to her. The argument becomes heated and Arata tries to stop it. Seiha adds commentary.
[12:11] 清葉: 落ち着きましょう。お父さんも来ることですし
Seiha: Everyone, calm down. Dad is coming soon.
{...some dialogues later. Basically the Father reveals that they are not related by blood except Minami and Shion who are twins. They are having a small discussion after dinner, Minami is praising the family cook's cuisine...}
[15:28] 万里: ホント南のその楽観的なところはお父さん似ね
Banri: In terms of optimism, Minami is just like Dad.
[15:32] 清葉: いえ。血のつながりはなかったので遺伝はないかと
Seiha: No. We are not related by blood, so it can't be hereditary.
[15:36] 新: 誰が笑えるんだよ
Arata: That's not funny.
[15:42] 謳華: パパが悪いわけじゃないのはわかるけどあんなこともっとタイミングとか
Ouka: I understand that we can't blame Dad, but couldn't he have chosen a better time?
[15:49] 清葉: いえ。タイミング的にはベストかと。いつまでも先送りにできるような話でもないですし。お母さんとの約束という話を踏まえてもことのの15歳の誕生日は妥当かと
Seiha: No. I think the timing is just right. This problem cannot be postponed indefinitely. Even if Dad made a promise to Mom, I think it's proper to announce it on Kotono's 15th birthday.
[16:06] 謳華: 理屈では分かる。でもダメ?寂しいって思っちゃ。今日まで隠してたなんて...パパにだまされてたのかって
Ouka: I understand. But am I not allowed to feel upset? We had been kept in the dark for so long... I feel as if Dad deceived me.
[16:22] 南: それは考えすぎじゃないかなー
Minami: You're overthinking it.
[16:24] 謳華: 分かってるけどさ!
Ouka: I know that.
[16:26] 清葉: 万里はどう思いますか。計算上ことのが紫雲寺家の一員になった時、万里は4歳だったのでは
Seiha: Banri, what do you think? When Kotono came to the Shiunji family, you should have been four years old.
[16:34] 謳華: そうよ!なにか記憶は
Ouka: Right, do you remember anything?
[16:37] 万里: それが私小さいころの記憶ほとんどなくて。うんー でも
Banri: I have almost no childhood memories. But...
[16:45] 清葉: 何かあるのですか
Seiha: Do you remember anything?
[16:47] 万里: あっいや...何でもない
Banri: Ah, no. Nothing.
[16:49] 謳華: 何よ言ってよ。今さら何言われても 驚かないわよ
Ouka: What is it? Just tell us. At this point, no matter what you say, I won't be surprised.

[16:54] 清葉: こんなメンタルの鍛えられ方は不本意ではありますが
Seiha: Although this kind of mental training is not what I wished for.
[17:04] 万里: 本当にささいなことだから。それにさ、今さら大したことじゃないでしょう。15年間一緒だったんだから血のつながりがないって言われてももうみんなをきょうだいじゃないなんて思えないって
Banri: It's really just some trivial matters. And at this point, it's not important anymore, right? We've lived together for 15 years. Even when told we're not related by blood, I can no longer not see you as my siblings.
[17:21] 清葉: まあ、それもそうですね
Seiha: That's true.
第1期第1話・清葉の台本、以上。/ Seiha's Lines in Season 1 Episode 1 End.