The OIKAWA Clan (及川氏)
The OIKAWA clan was a Japanese clan. It was a school of Seiwa-Genji (the MINAMOTO clan) (Settsu-Genji (MINAMOTO clan) MINAMOTO no Yoritsuna. It originated from Yorimasa MINAMOTO and was a branch of the Baba clan. The '及' of OIKAWA is not 'およぶ' but instead a variation of '笈' (or an abbreviation). It is also written as 笈川氏. It occupies in 282nd place in the nationwide population ranking; currently in Japan there are about 20,000 households, representing a total of seventy-eight thousand four hundred individuals.
The similar family names
As the names that are similar to '及川 and 笈川' (OHIKAWA), there are 追川氏 and 生川氏, but it is not well known whether they are just phonetic equivalents, related or totally different names.
There also exist 老川氏, 翁川氏 (OIKAWA, おいかは) and 小井川氏 (OIKAWA, をゐかは), but they seem to be different names.
MINAMOTO no Yorimasa (Yorimasa BABA) was a famous samurai warrior and poet who appears in "Heike Monogatari" (The Tale of the Heike) and is renowned for getting rid of the nue (a creature of Japanese legend). There is the bloodline from his son, MINAMOTO no Nakatsuna, as well as one from Nakatsuna's younger paternal half-brother, Masatsugu OIKAWA. Later, Nakatsuna's son MINAMOTO no Naritsuna governed OIKAWA manor in Tajima Province, Kinosaki County (near what is now Toyooka City) and identified himself as MINAMOTO no Naritsuna. This brought about the 'OIKAWA' family name. Naritsuna (Moritsuna)'s uncle, Masatsugu, identified himself as OIKAWA, whereupon Naritsuna and the Masatsugu bloodline flourished in Oshu, but later it went to ruin and consequently the Naritsuna bloodline flourished instead of this.
Masatsugu was a descendant whom his father Yorimasa left when he went to Oshu, leaving the capital, and among the families he became a pioneer of localization in Oshu. Masatsugu was probably more than 40 years younger than his older paternal half-brother Nakatsuna and was probably younger than his cousin Naritsuna. Masatsugu identified himself as being of the OIKAWA clan, meaning that he followed Naritsuna as part of the same family. Apparently, Naritsuna also followed the Kamakura bakufu (Japanese feudal government headed by a shogun) because Naritsuna's elder brother, MINAMOTO no Aritsuna, joined MINAMOTO no Yoritomo when Yoritomo rose up in arms (the place name 'OIGAWA village' in Atsugi City, Kanagawa Prefecture, seems to have had a relationship with Naritsuna or Naritsuna's son Mitsutsuna OIKAWA, but formerly it was also written as '及河' and was properly read as 'OIGAWA' in a dull sound. Today, seven percent of all OIKAWA clan members are residents of Kanagawa Prefecture. Mitsutsuna's offspring Mitsushige OIKAWA became a retainer of the Yuki clan in Shimousa Province and was localized in Shimousa, and Mitsushige's offspring Mitsufusa OIKAWA became a retainer of the Shirakawa Yuki clan and obtained territory in Oshu (Fukushima Prefecture) (there is the place name 'Oikawa village' in Kitakata City, which may suggest that there was a relationship with the Oikawa clan in those days, but the birth of the place name was after the Shoo era and previously it was called Nikkuni).
A vassal of the Oshu Kasai clan
The OIKAWA clan became a retainer of the KASAI clan, which had influence from the southern part of Iwate Prefecture to the north part of Miyagi Prefecture but, due to the consequent development, was divided into three family lines.
The Sadatsugu family line
Initially, Masatsugu's grandson Sadatsugu OIKAWA became a retainer of the KASAI clan in the earliest time, but he was exterminated due to the reasons described below.
The Yoritada family line
Next, there was Yoritada OIKAWA, who became a retainer of the KASAI and moved to Oshu as one of Mitsutsuna's offspring.
The Mitsumura family line
This was the family line that became a retainer of the KASAI at the end. Mitsufusa OIKAWA's great-grandson Mitsumura OIKAWA was killed in the Yuki War, so that the line temporarily went to ruin; Mitsumasa's son Mitsumura OIKAWA lost his territories, ran away and sought refuge in the KASAI clan. Mochinobu KASAI gave territories to Mitsumura and made him his retainer (at that time, many families seemed to remain in Shimousa; the OIKAWA clan concentrates in the northern part of Chiba Prefecture, and currently six percent of all OIKAWA clan are residents of Chiba Prefecture).
In the mid-fifteenth century (the Muromachi period), the offspring of Sadatsugu OIKAWA raised a rebellion against the KASAI clan, but Mitsumura suppressed it. Thus the Sadatsugu family line was destroyed, whereupon the Mitsumura family line took over; the OIKAWA clan gave rise to many branches, spread and increased throughout Oshu. Currently, the OIKAWA family name centers on the middle and southern parts of Iwate Prefecture and the northern part of Miyagi Prefecture (53％ of all OIKAWA clan live in both prefectures), but was scattered around the prefectures of the Tohoku region such as Aomori, Akita, Yamagata and Fukushima.
During the early sixteenth century (the mid-Sengoku (Warring States) period), Mitsumura's grandson Shigetane OIKAWA fought with the Esashi clan but was defeated, and consequently the Mitsumura family line went to ruin. Instead, Yoritada's offspring Yoritaka OIKAWA succeeded to the castle.
During the mid-sixteenth century (the late Sengoku period), in the time of Yoriie OIKAWA, a grandson of Yoritaka, they were deprived of the territory by his master, the KASAI clan; subsequently, the family line went to ruin and took up farming again. Shigeuji OIKAWA survived as a retainer of the KASAI clan although the Shigetane family line declined, but later, during the time of Hideyoshi TOYOTOMI, the KASAI clan was destroyed by Hideyoshi; all the family became ronins (masterless samurai), and some of them joined Kasai-Osaki-ikki (the revolt of the former retainers of the Kasai and Osaki clans). Eventually, some of them became retainers of the DATE and NANBU clans, like Shigehide OIKAWA (an offspring of Mitsumura) or Nobutsugu OIKAWA (a son of Yoriie). (Today, as for the OIKAWA family name, thirteen percent of it is in Hokkaido, seven percent in Tokyo and some of it is in the prefectures of Ibaragi, Saitama and Shizuoka).
In medieval times they were localized in Oshu as retainers of the KASAI clan; the three family lines rose and fell alternately, had conflicts with neighboring forces and spawned many branch families.
The samurai of the YUKI clan's retainer
Mitsushige OIKAWA, Mitsufusa OIKAWA, Mitsumasa OIKAWA.
The samurai of the KASAI clan's retainer
Sadatsugu OIKAWA, Shigeuji OIKAWA, Shigetane OIKAWA, Tsunashige OIKAWA, Mitsumura OIKAWA, Yorio OIKAWA, Yorikane OIKAWA, Yoritaka OIKAWA, Yoritada OIKAWA
Those who raised a rebellion against the KASAI clan
Shinano SHISHIORI, Yoriie OIKAWA
After the decline of the KASAI clan, those who became retainers of the DATE clan
Shigehide OIKAWA, Nobutsugu OIKAWA
Naritsuna OIKAWA, Masatsugu OIKAWA, Mitsutsuna OIKAWA, Naritsuna OIKAWA
The family crests
Various crests were used depending on the family, but ultimately there were many Katabami (cuckooflower) crests.
Maruni Ken Katabami' crest/'Ken Katabami' crest
Katabami' crest/'Maruni Katabami' crest/'Ishimochi Jinuki Katabami' crest/'Maru ni Chukage Ken Katabami' crest (examples of Iwate Prefecture)
Additionally, there are many kinds such as the Paulownia style, Boston ivy style and so on.
The family names derived from the OIKAWA clan
There are branch families from OIKAWA clan such as 'OTOKOZAWA clan,' 'MASUBUCHI clan,' 'SHISHIORI clan,' 'ONODERA clan' (ONODERA of the MINAMOTO family) and so on.