ナインソールというゲームに触発されました（正直者）
おまけの２ｐ漫画もあります↓
FANBOX： https://ie1.fanbox.cc/posts/9312089
Fantia： https://fantia.jp/posts/3256525
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～～～～～～～The following is for translation～～～～～～～～
１ｐ
これが『内丹術』の修行だ。体内の気を養い一点に凝縮させ、不老不死の霊薬『内丹』を己の身中に作り出す
ぐぬぬ…
見た目よりもきついだろう。そのうえ膨大な時間も必要になる。
…まあ実を言うともっと短時間で、簡単な修行があってだな…
なんだよ…！そっちを教えてくれよお師匠…！
…ん………うむ……まあ…うん………いいだろう…

おいおいおい！嘘だろ！？マジかよお師匠！？
嘘ではない。本当にこれが最も効率的な修行なんだ…（房中術とも言ってな…）
…とはいえ…『ババア』が相手では気が進まんだろうと思ってな…
先にあっちの大変さを知ってもらったというわけだ…
……………初めてがこんな……綺麗な人なら…むしろ歓迎です…
…………そうか…

I was inspired by the game Nine Souls (honestly speaking)

There's also a bonus 2-page comic below ↓
FANBOX： https://ie1.fanbox.cc/posts/9312089
Fantia： https://fantia.jp/posts/3256525
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～～～～～～～The following is for translation～～～～～～～～
１ｐ (MTL)
This is the training of "Internal Alchemy." It involves cultivating the vital energy within the body, condensing it into a single point, and creating the elixir of immortality, "Internal Alchemy," within oneself.
Grrr...
It's harder than it looks. And it takes a tremendous amount of time.
...Well, to be honest, there's a much shorter and easier training method...
What?! Tell me about that, Master!
...Hmm...Um...Well...Okay...Alright...

Hey, hey, hey! You're kidding, right?! Are you serious, Master?!
It's not a lie. This really is the most efficient training method... (It's also called the Art of the Bedroom...)
...However...I figured you wouldn't be keen on an "old woman" as your partner...
So I wanted you to experience the difficulties of that first...
...If my first time is with someone this...beautiful...I'd actually welcome it...
...I see...