

Each student had to face him about four times over the three days, though
some never made it past the first day due to Oyama's powerful blows. Legend
even has it that Oyama was willing to go for a FOURTH day, but no one else
was willing or able! This took place no long after he had completed his
mountain training.

At first, the fights could be completed over two days if so desired
by the person doing it, but after 1967, Mas Oyama decided that they should
all be fought on the same day. In addition to the basic requirement of
100 fights, other requirements are that the competitor must clearly win
at least 50%
of the fights, and if knocked down, should not stay down for longer
than 5 seconds.
In Australia, and possibly elsewhere, the 50 man kumite is a lesser (but still no mean achievement) feat that can be attempted.
In Great Britain, and anywhere else under the aegis of Hanshi Steve
Arneil, anyone can choose to do any number of fights e.g. 10, 20, 30 ,
40, 50 etc.... and he or she will get a certificate for this achievement.
This in recognition that, while not everyone maybe able to meet the ultimate
Kyokushin benchmark of 100 fights, personal bench-marks are just as important
an attainment. After all, even 10 knockdown fights in swift succession
can come to as much as half an hour of solid fighting.

Initially, people had the choice do it over two days, with 50 fights per day, but later it became compulsory to do it all in one day.
Steve Arneil (1965) Steve Arneil of Great Britain (now 8th Dan) was the very first, and he did them all in one day (pers.comm). He is now the head of the International Federation of Karate (IFK) based in the UK, and which is not affiliated with the Honbu in Japan.
Howard Collins(1967) He was the first to do it compulsorily in one day.
Miyuki Miura (Friday the 13th, April 1972) The first Japanese to do it in one day, he now heads the Midwest Headquarters of the World Oyama Karate offshoot.
Akiyoshi
Matsui (1986)
Akiyoshi Matsui is the (vigourously disputed) successor to Mas Oyama as
kancho or head of the International Karate Organisation (IKO) (listed as
IKO(1) in the
this website - Shah). He was the winner of the 1985 and 1986 Japanese
Open Championships, and the 1990 4th World Open Karate Tournament.
Hajime Kazumi (Sat, 13th March,1999) Hajime Kazumi completed his 100 man kumite at the new IKO(1) Honbu. Results were obtained from the official IKO(1) site and are as follows:Ippon Victories- - - - - - - - - - - - - - - - - - - -- - - - - - - - - - 46
Win by decision (includes Waza-ari)- - - -- - - - - - - - - -29
Draws- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -13
Losses by decision- - - - - - - - - - - - - - - - - - - - - - - - - - - 12
- -(includes for losses due to dropped grip-sticks)
Losses by Ippon- - - - - - - - - - - - - - - - - - - - - - - - - - - - - - 0
________________________________________________
Total - - - - - - - - - - - - - - - - - -- -75 wins, 13 draws and 12losses
Time per Kumite 1 minute 30 seconds
Time Started 11:38
Time Finished 15:42
Total Fighting Time 3 hours 20 minutes 40 seconds
Total Spending Time 4 hours 4 minutes
Results 58 wins, 42 draws, no losses
Ippons: 16 (Ippon: 2, Awase-Ippon: 14) Wins by decision: 42 (Waza-ari: 15)

A World Championship tournament might consist of 7 or 8 rounds of tough kumite, and with allowances for 4 extensions and no byes, this would come to just over half an hour of fighting. There would however be lengthy rest breaks between rounds, with time to tend to injuries. Consider a boxer going 100 rounds non-stop with no breaks and with a new opponent each round, and with the requirement of winning at least 50 of these rounds.
Imagine up to 4 hours of non-stop full-contact kumite, bearing in mind
that in Kyokushin tournaments we are only allowed mouth and groin guards!
To be fair, if the candidate is good and knocks his opponent down fast
enough, the round can be over in less than full time. It seems unlikely
that anyone will ever again achieve the same as Mas Oyama did with his
300 rounds!