Embedding Text in Text in Japanese Poetry

There was no systematic cryptography in Japan before she opened the country to the Western world in the nineteenth century. But some techniques in poetry are somewhat similar to concealment cipher.
Acrostics, called oriku in the field of Japanese poetry, are well-known (Wikipedia).

The other day, I learned of a more ingenious technique called 物名 (mononona or butsumei, "a thing's name") or 隠し題 (kakushi-dai, "a hidden theme") in an essay in a newspaper (The Asahi Shimbun, 22 December 2023).

One poem (tanka) is
茎も葉もみな緑なる深芹は
　洗ふ根のみや白く見ゆらむ
(Kuki mo ha mo, mina midori naru fukaseri ha,
arafu ne nomi ya shiroku miyu ramu.)
The latter part ("arafu ne nomi ya shiroku miyu ramu") means "is it only the washed root that looks white?" but a part of it can be parsed in a different way: "Arafune no miyashiro", which means something like "the sacred shrine of Arafune."

The tanka which hides the longest hidden text found by 小林祥次朗, "発掘　日本のことば遊び" (2002-10-28, JapanKnowledge) is:
時雨する川辺の紅葉出でてまづ
　橋の上の木濡れつつぞ見る
(Shigure suru kawabe no momiji ide te matsu
hashi no uhe no ki nure tsutsu zo miru.)
The text in bold is part of a phrase meaning "first look upon a tree while getting wet", but can be parsed "matsuhashi no uhe no kinu" (a kind of ancient court attire).