Anybody who got into Tokusatsu must have heard his name. I’ll leave a perfunctory introduction to Wikipedia in English.
On this article I’ll write about non-translated article on him and also introduce some quote from some magazine’s article or something.
First of all why he chose stuntman as his profession? The answer is quite simple. He admired Hiroyuki SANADA, a famous Japanese action star, who had been affiliated with J.A.C(Japan Action Club). In the early of the 80’s Mr.Sanada was a kind of icon of action star from J.A.C and considered as a student of Sonny Chiba, who founded Japan Action Club. Anyway his great popularity attracted many young people and his influence was reflected in the numbers of applicant for Japan Action Club. In those days J.A.C accepted application once a year and it got over 1,000 applicants every year. Applicants are tested their physical ability and acting skills. Fortunately Mr.Takaiwa passed the audition and became one of the promising stuntmen
His first appearance on TV was in 1989 as Riderman in Kamen Rider Black RX. Three years later he made full-blown debut as Dragon Ranger in Kyoryuu Sentai Zyuranger.

Of all his great talents, it is his acting skill that makes him unique. One of the outstanding achievements in his career is portraying almost all of Heisei (New Generation) Riders, and it is well known that he impersonates the actors of each rider completely on the basis of the observation of their subtle gestures and movements. He was highly praised especially for role of Kamen Rider Den-O in which he had to portray a character who had several completely different personalities. According to him, he began to take into consideration personality of an actor who plays “a hero before transformation” when he acted Megablue in Denji Sentai Megaranger. Since then he has been trying to reflect before-transforming actors’ personalities in the movements as “a hero after transformation.” As you might know, his great work in Kamen Rider Den-O could be regarded as the trigger of his getting popularity and nation-wide fame, and he himself said that Den-O was a compilation of his career for as long as twenty years.
His great acting skill includes his elegant ad-lib playing. He often says lines that are not on a script. One of the famous episodes is going back to 2002, when he was acting Kamen Rider Ryuki. In episode 1, there’s a scene where Ryuki’s shouted “Oretaa! (Oh! It’s broken)” when his sword was destroyed. At first there’s no lines in this scene, however Mr.Takaiwa shouted “Oretaa!” with showing panic gesture as an ad-lib. This ad-lib lines described the director’s image of Ryuki so wonderfully that the lines were added to the script on the spot. The director said Takamasa Suda as Shinji Kido was helped to prepare for his role, a little jocose guy by this scene. Anyway this is only one example on which his creativity is reflected. Actually many staffs and his co-workers always stare at his acting with expectation of something original and fresh coming out. Even actors during break time also try to learn from him. As a result the scene where Mr.Takaiwa appears is now called “TAKAIWA ON STAGE.”
Incidentally, Kamen Rider Ryuki was supposed to fight in the Mirror World, a parallel dimension opposite to our own, so background must be mirrored image. To visualize this “left-right reversal world”, the filmed picture was flipped horizontally in the process of editting. As a matter of course all of the characters, riders and monsters in the Mirror World had to hold their weapon in the opposite hand. Mr.Takaiwa, who was right-handed had to fight holding a sword in his left hand. According to one interview article, he had a lot of trouble with this, and couldn’t help hoping the staff created a set of background which is left-right reversal so that he could do sword fighting easily.
These stories are only few parts of a lot of episodes which tell you his greatness. As one of Japanese Tokusatsu fans I think he is a one-in-a-million person.

I’d like to introduce some episodes related to Mr.Kamen Rider. These episodes are translation from Japanese Wikipedia.

Episodes of Kamen Rider 555
He has acrophobia in spite of being a stuntman. In Kamen Rider 555, there was a scene where Kento Handa as Takumi Inui rode a roller coaster. However Mr.Handa also had acrophobia, so he asked Mr.Takaiwa to double. He managed to do it trembling with fear. Besides that he had acted Red rangers in stage show at Tokyo Dome City Attractions (ex.Korakuen Yuenchi), he had to ride a roller coaster standing up. In those days that was the standard way of Red ranger’s making his appearance.

When the eyes of faiz’s mask were emitting, a stuntman inside the costume couldn’t see anything due to the structure of the mask. So he had to do action without eyesight. Makoto Itoh, who acted Kaiza had the same problem. However when Eitoku acted faiz in Kamen Rider Decade, faiz’s mask had been modified to allow a man inside to see outside the mask.

During filming of faiz, his father fell critically ill. Takeshi Miyazaki, the action director and other staff suggested strongly that he should return to see his father, and proposed that they would arrange for someone else to be in his place. However he didn’t want somebody else to be faiz because he was worried that faiz acted not by him would bother the viewers by a feeling of strangeness. As a result he didn’t witness his father’s last.

Episodes of Kamen Rider Den-O
According to him, he was bad at dancing. He had a hard time in the filming of Magiranger’s ending and Den-O Gun Form, where he had to dance. In his interview article he said that he and Toshihiro Ogura, who acted Ryutarosu often mumbled “Takeru Sato, whose hobby is break dance is quite a good dancer. His dance is too nice to imitate”

On parents’ day in the kindergarten where his son went, he put on a costume of Momotaros and made the children delight.

On the very first day of the filming of the movie titled “Saraba Den-O Final Countdown”, he fell over because of lack of air and high temperature. He was supposed to action for as long as two minutes, which was quite hard under the condition of wearing a costume of Momotaros. This incident was on Toei’s official website under the title of “Takaiwa Sanketsu Jiken. (Takaiwa fell over a lack of air)”