What does Kasai mean?


(West Katsushika)

Kasai Rinkai is famous for its nature preserve, and in particular, its aquarium.
Kasai Rinkai is famous for its nature preserve, and in particular, its aquarium.

What does Kasai mean?

Kasai is a general term used to describe the southern portion in Tōkyō’s 江戸川区 Edogawa-ku Edogawa Ward, ie; the portion that lies on Tōkyō Bay.

Let’s Look at the Kanji

kuzuJapanese Arrowroot,
a reed-like grass that grows in wetlands
西sai, nishiwest

Nothing in this article will make sense if you haven’t read yesterday’s article on Katsushika.
As far as I know, today there is no area named Kasai, but there are train stations, bus stations and facilities that bear the name. Here are a few examples:

北葛西Kita-KasaiNorth Kasai
南葛西Minami-KasaiSouth Kasai
東葛西Higashi-KasaiEast Kasai
西葛西Nishi-KasaiWest Kasai
中葛西Naka-KasaiMiddle Kasai
葛西臨海Kasai RinkaiKasai Oceanfront
葛西海浜Kasai KaihinKasai Seaside

The last two names are in reference to a park and nature preserve[i].

Kasai Rinkai Park and Kasai  Kaihin Park
Kasai Rinkai Park and Kasai Kaihin Park

So, Why is Kasai called Kasai?

The name Katsushika is attested in a census of the area in 721[ii]. It’s listed as part of 下総国葛飾郡Shimōsa no Kuni Katsushika-gun Katsushika District, Shimōsa Province[iii]. If you look at a modern map of Tōkyō, you’ll see that Edogawa is located south of Katsushika. This caused me to wonder, why is the southern area bear the name “west” when it’s clearly south?

Above the area marked #1 down to the white area (Tokyo Bay) is the former Katsushika District.
Above the area marked #1 down to the white area (Tokyo Bay) is the former Katsushika District.

But if you remember from yesterday’s article, the whole area from present Katsushika Ward to the bay in southern Edogawa Ward was part of the ancient Katsushika District.

Well, it turns out that by the Kamakura Period, the course of the 江戸川 Edo-gawa Edo River had changed the shape of the terrain[iv]. This prompted the creation of 2 new administrative districts. The west bank was called 葛西郡 Kasai-gun Katsu(shika) West District and the east bank was called 葛東郡 Katō-gun Katsu(shika) East District[v]. So in short, Kasai is a vestige of this former sub-district which doesn’t exist today.

There's little physical evidence remaining of the Kasai clan's presence in the area.
There’s little physical evidence remaining of the Kasai clan’s presence in the area. Let’s find out why!

A Side Note on pre-Tokugawa Noble Families Operating in the Area

I don’t like getting into genealogies of Japanese noble families because it’s kinda boring and I get really fucking confused after a while. But I thought this was interesting because it ties into the place names of Toshima and Edo.

The 桓武平氏 Kammu Heishi Kammu Taira Clan was established by the Emperor Kammu in the early 800’s. He granted the clan name Taira to some of his grandsons. A new branch was established when someone of this line was granted control of the Chichibu Province (present day western Saitama). The newly established clan took the name of their fief and became the 秩父氏 Chichibu-shi Chichibu Clan. In the 12 century, a member of the family was granted a fief in Edo. This family assumed the name of their new holdings and became the 江戸氏 Edo-shi Edo Clan[vi]. Not long after that, a member of the Edo Clan was given control of the Kasai District of Shimōsa Province. And yes, you guessed it, this branch assumed the name of their new territory and became – wait for it……………… the 葛西氏 Kasai-shi Kasai Clan!

Family crest of the Taira.
Family crest of the Taira.

Now remember, the Taira Clan were descendants of the Emperor Kammu, but by the 12th century, the newly established 葛西家 Kasai-ke House of Kasai[vii] were merely low ranking vassals of another powerful clan in the area. And who might that family be? Why, it was none other than the 豊島氏 Toshima-shi Toshima Clan of 豊嶋郡 Toshima-gun Toshima District, Musashi Province.

Long time readers will know the eventual fate of the Toshima Clan[viii] and you might be tempted to assume that the Kasai met the same fate. But pre-Edo Period samurai were a wily bunch always looking for opportunities to increase their wealth, power, and influence. The Kasai raised an army and assisted 源頼朝 Minamoto no Yoritomo Minamoto Yoritomo in the final subjugation of the Taira[ix]. They were rewarded with various holdings in the Tōhoku region. To this day, family names with the kanji 葛西 are common in Aomori, Miyagi, Fukushima, and Iwate[x].

Tohoku... yeah!
Tohoku… yeah!

Back to the Kasai Area!

After the Kasai family left the region it came under the control of the 千葉氏 Chiba-shi Chiba Clan (namesake of modern Chiba Prefecture) and after that the 後北条 Gō-Hōjō the Hōjō Clan[xi]. After the destruction of the Hōjō, the area finally came under the control of Tokugawa Ieyasu and remained stable until the Meiji Restoration.

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[i] I couldn’t find good information, and I may be wrong on this, but I’ve heard that the Kasai Rinkai Park area was a lower residence of a branch of the Matsudaira family (an Edo Period landfill). Again, I’m not clear on the details, but I believe the Kasai Kaihin Park area was also an Edo Period landfill and they appear to be breakwaters, which would have protected the lord’s residence on the mainland. I could be wrong on this.

[ii] The document is the 下総国葛飾郡大嶋郷戸籍 Shimōsa no Kuni Katsushika-gun Ōshima-gō Koseki Census of Ōshima Hamlet (Katsushika District, Shimōsa Province). Here’s a description of the document in Japanese.

[iii] For those of you who haven’t been keeping up, please see my articles on Ryōgoku and Toshima and Musashi.

[iv] The Edo River, by the way, is a tributary of the 利根川 Tonegawa Tone River. The Tone River was known as this sort of uncontrollable beast. The river was notorious for flooding, then changing directions. It seems that the Edo River, being the proverbial little brother of the Tone River, had a similar reputation as a shit stirring river.

[v] The kanji are reversed, but this place name is preserved as 東葛 Tōkatsu, a region in present day Chiba.

[vi] If you remember my post on Edo, you’ll remember the Edo Clan. You’ll also remember how they were later forced to change their names to 北見氏 Kitami-shi Kitami Clan. Eventually, the Tokugawa shōgunate abolished the family line for unforgiveable transgressions.

[vii] Kasai Family to use a non-Game of Thrones term.

[viii] Please read more about the Toshima in these articles: Shakujii, Nerima, and Nerima.

[ix] Yes, folks you read that right.

[x] Apparently there are 4 variants of this kanji combination, the non-Kasai readings are said to have originated in Tōhoku: Kasai, Kassai, Katsusai, Katsunishi.

[xi] This clan, the so-called Late Hōjō, were a bunch of assholes. But they were tough assholes. Their resistance to Hideyoshi’s unification efforts eventually led to their complete annihilation. That action also led to Tokugawa Ieyasu being given the 8 Kantō Provinces… and the rest, as they say, is history.

4 thoughts on “What does Kasai mean?

    1. Kansai and Kanto are opposites.
      Kansai is something like “the west connection” and Kanto is something like “the east connection.”

      They are references to the geopolitics of the late Heian Period and the rise of the samurai class.

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