I'm afraid that I cannot see the article you linked to dwk but I can at least add some context on Ishii's career, at least as far as I am aware of it.
Takashi Ishii is probably best known in the West for his mid-90s yazkua series
Gonin (with an all star cast including Takeshi Kitano, Naoto Takenaka and Jinpachi Nezu) and
Gonin 2. I see that his last film from 2015 is a third entry in the series,
Gonin Saga. His other crime series from the same period was the two films in the
Black Angel series.
Probably his most available film in the UK though was his 2000 horror-drama film
Freezer (aka Freeze Me) which Tartan Video released through their Asia Extreme line. This may actually be a bit closer to Ishii's usual territory than his yakuza dramas since this is a rape-revenge film about a woman who kills her attacker and sticks his body in her freezer to dispose of it piece by piece, but inevitably finds (like that video nasty Cannibal Man) that more and more people start calling around to her apartment trying to find out where their friend disappeared to and she has to take care of them as well! Eventually she is attracting attention for the multiple freezer cabinets she is filling her apartment to the brim with! It all builds to a quite haunting (but quite darkly amusing as well!) final shot.
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The reason why I say that this may be more familiar territory for Ishii is that he was originally a manga artist whose series about sexualised rape and the psychological traumatic fallout from that, called
Angel Guts, became one of the most notorious sub-series within Nikkatsu's Roman Porno period. In all five films were produced from 1978-1988 (with a sixth entry made independently post-Nikkatsu in 1994). Each film is a standalone piece with a different set of characters and situation, although the main female character is always named Nami Tsuchiya and her various male love interests are all named Tetsuro Muraki. Although to call them 'love interests' rather stretches the term since they run the gamut from straightforward assaulters to
overly protective and possibly Incestuous brothers (NSFW) to rival reporters, to just the pervert across the way spying on a schoolgirl doing something incredibly naughty involving an egg, a condom and a sharpened pencil instead of getting on with her homework!
After providing the source material and screenplays for the first four films (including the astonishing third film of the series Angel Guts: Nami, which goes into delirious Argento-horror style territory in the final act as the mercenary female reporter tracking down and using rape victims for her sensationalised articles in her tabloid magazine gets the tables turned on her in the bowels of a hospital when her latest interviewee/victim turns out to have been driven psychotic by her assault. This then ends in
(spoiler)Nami having a complete breakdown and becoming the perfect subject of one of her articles by fantasising in a dream sequence of her uncaring colleagues in her office pelting her with abuse), Ishii got the chance to direct the fifth entry in the series in 1988, Angel Guts: Red Vertigo.
Red Vertigo is a really interestingly dark and cynical film in itself, as after being assaulted by a patient whilst working as a nurse at her hospital and then due to that deciding to go home early to her photographer boyfriend only to find him in bed with his latest model, Nami leaves her apartment in tears and has an already bad day compounded by being run down by Muraki! Muraki himself (in an early role for Naoto Takenaka) is on the run from loan sharks and angry bosses and having picked Nami up from the road and placed her in the passenger seat, does the only sensible thing one could do: falls in love with the unconscious woman and decides to take her to an abandoned Air Force base he knows (more on which later!) where these two people who feel rejected by the world start up an intensely sexual Realm of the Senses (or Night Porter)-style relationship until inevitably the outside situation has to intrude into their sealed off world to end it all.
Also in 1988 Ishii wrote the screenplay for Toshiharu Ikeda's utterly bonkers slasher film
Evil Dead Trap (Ikeda had previously directed the fourth entry in the Angel Guts series, Red Porno. aka the one with the egg and pencil and the absolutely no homework getting done!), which although unconnected (though the main characters
are named Nami and Muraki :-k ) uses the same abandoned US Air Force base location for its action.
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So that mid-90s period of yakuza and action films more mainstream 'respectability' may be his highest profile period after spending the early 90s trying to continue the Nikkatsu Roman Porno film-style work but in the independent sector. With Freezer however there was a turn back to the darkly sexual material, and during the 2000s Ishii wrote the screenplay for and directed the first two films in Toei's 'reboot' Flower & Snake S&M-themed series (which had previously been a film in Nikkatsu's Roman Porno series in 1974), and appears to have continued to have made darkly sexual dramas up to the mid-2010s. I would love to see some of these at some point, such as 2007's wonderfully titled
"The Brutal Hopelessness of Love" (maybe a follow up to Toshiharu Ikeda's 1993 "The Brutal Insanity of Love"?) which appears to go back to naming the main character Nami Tsuchiya again.
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In terms of availability, Ishii has fallen out of view a bit. The first two Gonin films were released on DVD in the early 2000s (the first film in particular was in the right place at the right time and appears to have benefited from the interest in Takeshi Kitano's work post-Sonatine breakthrough in the West and probably got picked up by distributors as another "Beat" Takeshi film even though Kitano is just in an acting role here) but are long out of print. Similarly the Tartan Asia Extreme mid 2000s edition of Freezer (which may be the best entry point for those new to his work) is getting rare too, although it looks as if there are still a few copies still remaining on Amazon.
I got to see the the Angel Guts films through the Artsmagic boxset released in the US in the mid-2000s (which has some great Jasper Sharp commentaries, which is where a lot of my above information on Ishii is coming from! Though there is a bit of dead air during the egg, pencil and homework left undone scene of Red Porno after Sharp says that he prefers not to speak over the scene and will let it speak for itself!). There were some standalone editions of the films released as well, but it appears that they are all long out of print, and Artsmagic as a company seemingly disappeared around the same time that Tartan did.
I have my fingers crossed that some of Ishii's early Nikkatsu Roman Porno films that he wrote will appear in the Impulse Pictures line of releases in the US (one actually already has, as Zoom Up: Beaver Book Girl was based on his manga. Which makes for a good companion piece to Angel Guts: Nami, in that it involves a mercenarily callous adult photographer getting much more than he bargained for with his latest assignment!), and I would like to hope that a company like Arrow might be able to do a Gonin boxset, or even a Flower & Snake reboot boxset at some point.
But for now there is nothing in the UK and in terms of the US (along with Zoom Up: Beaver Book Girl on DVD) the only currently available Ishii-related work is the Unearthed Films Blu-ray of Evil Dead Trap.