Ki-100 is not high performance, and was not the best B-29 interceptor. What it was, that other Japanese planes built at that time were not, is reliable.
The J2M 'Jack' Raiden was the best B-29 interceptor.
While the Raiden was superior in B-29 interception, the K-100 was superior overall. So lets change my rationale to overall performance.
"The Ki-100 made its combat debut on the night of 9 March 1945[7] and suffered its first loss on 7 April 1945, when a Ki-100 flown by Master Sergeant Yasuo Hiema of the 18th Sentai was shot down by a B-29 after "attacking the formation again and again".[7][N 1] Allied aircrews soon realised that they were facing a formidable new fighter[12] Although far fewer Ki-100s were available than the Ki-84s, it was considered one of the most important fighters in the inventory. However, during interception of the high-flying B-29s (the B-29 raids soon became low-level missions) the new Japanese fighters struggled as the Ha-112-II engine's performance decreased at high altitudes. The most effective way to attack the Superfortress was by making very dangerous head-on attacks, with the fighter hanging its approach path as it neared the bomber. A failure while attempting this was deadly, because of the concentration of defensive fire from the bombers. In this type of combat, the Navy's Mitsubishi J2M Raiden was superior.[13]
During March and April 1945 experienced instructors from the Akeno Army Flying School flew the Ki-100 in extensive tests against the Ki-84, which was considered to be the best of the JAAF fighters then in operational service. Their conclusions were that, given pilots of equal experience, the Ki-100 would always win in combat.[4] From Mid-April, Major Yasuhiko Kuroe, a highly experienced combat veteran was placed in charge of a "flying circus" made up of captured Allied aircraft, including a Mustang which had been captured in China. This "circus" travelled to various operational fighter bases throughout Japan and was used to train pilots in the best ways to combat enemy aircraft.
On 25 July 1945, 18 Ki-100 fighters from 244th Sentai encountered 10 Hellcats of the light aircraft carrier USS Belleau Wood's Fighter Squadron 31 (VF-31) in an air battle where the Ki-100 pilots claimed 12 victories with only two losses. Claims and counter-claims regarding the true results still arise around this action. The American claims were two Hellcats and two Ki-100s, including Major Tsutae Obara's Ki-100 and Ensign Edwin White's Hellcat which collided, killing both pilots.[14] USN records for 25 July 1945 reflect the loss of two aircraft, both F6F-5's, by VF-31, #78228, piloted by ENS Edwin R. White and #77489, piloted by ENS Herbert L. Law[15]
After the bombing of the Kagamigahara plant and the slow deliveries of components by the satellite plants, production rates of the Ki-100 began to fall more and more, and in the period between May and July, only 12 units were delivered. Finally, production ended due to the bombing, with only 118 units of the Army Type-5 Fighter Model 1b delivered.
The last loss of a Ki-100 occurred on 14 August 1945, a day before the surrender of Japan, when Sergeant Major Fumihiko Tamagake of the 244th Sentai was shot down by a Mustang.[11]
An overall assessment of the effectiveness of the Ki-100 rated it highly in agility, and a well-handled Ki-100 was able to outmanoeuvre any American fighter, including the formidable P-51D Mustangs and the P-47N Thunderbolts which were escorting the B-29 raids over Japan by that time, and was comparable in speed, especially at medium altitudes. In the hands of an experienced pilot, the Ki-100 was a deadly opponent; the Ki-100 and the Army's Ki-84 and the Navy's Kawanishi N1K-J were the only Japanese fighters able to defeat the latest Allied types.[16]"
Francillon, René J. Japanese Aircraft of the Pacific War. London: Putnam, 2nd edition, 1979. ISBN 0-370-30251-6
Picarella, Giuseppe. "Database: Kawasaki Ki-100. Article, scale drawings and cutaway." Aeroplane magazine, Volume 33, No 11, Issue No 391, November 2005. London: IPC Media Ltd.
Sakaida, Henry. Japanese Army Air Force Aces 1937-45. Botley, Oxford, UK: Osprey Publishing, 1997. ISBN 1-85532-529-2
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
I would still add it before the Beau.