Usage of よう without に particle

Question

みなさん、こんにちは！

So, I am a beginner. I have just started reading my first manga in Japanese, 鬼滅の刃, and I've encountered a sentence which I don't really understand the grammar for. Here it is:

丸腰{まるごし}​であるのを悟{さと}られないよう振{ふ}りかぶった体勢{たいせい}で手元{てもと}を隠{かく}す

I've understood it to mean roughly:

He hid his grip so that I would not realize that he was unarmed.

which makes sense in context. The grammar that confuses me is the usage of 「よう」 without any particle afterwards. I am familiar with 「ように」 and 「ような」 but I am not quite sure if I am missing something here.

Was 「に」 simply omitted in the sentence above? If that is the case, is such usage common or is it a more dated style?

Here's the page in question with some extra dialog: https://i.sstatic.net/GhSR9.jpg

Answer 1

「Phrase A + よう + Phrase B」

「Phrase A + ように + Phrase B」

In basic meaning, the two patterns above are identical.

The only difference is that the second one using 「ように」 is more casual and conversational than the first with 「よう」. For that reason, 「よう」 tends to be used more often in writing.

The sentence you have quoted sounds non-conversational; therefore, 「よう」 fits better there.

「ような」, BTW, is not an option here as it needs to be followed by a noun.

「よう」 and 「ように」 are followed by verb or adjective phrases (or whole mini-sentences).