the internet archive is your friend when doing factual research on many a topic:
https://archive.org/
in this case, entering shuttle-japan.com in the box and choosing any number of likely dates would give you your answer: december 5, 1998
example:
https://web.archive.org/web/19991127163735/http://shuttle-japan.com/BU/e/BU.html
as you can see from this page, the bukkake summit series started on october 14, 1998 when bu-01 and bu-02 were both shot in one day. many of the same men were used in the second video and as a result, the machine-gun assault of sperm in the first was reduced to a wet-powder dribble in the second. the producers complained. so a two week hiatus ensued in order to give the team time to recover. even that proved insufficient; for many of the volunteers were concluding that it wasn’t quite as much fun to stand around masturbating in front of a hundred other guys (and then blowing your load on camera for the national audience) as they originally thought it would be. the end of the line was out on the sidewalk, and the ones there had to keep answering embarrassing questions of passers-by (hey, what's going on? what are you doing?). so replacements had to be recruited. by the time bu-04 was shot, they were settling in to a regular once-a-month schedule.
school certainly has changed since i was a student. i would have been expelled for merely suggesting a research paper on bukkake… even if bukkake had existed back then. regardless, i applaud your effort. i remember my first history teacher (the football coach really… but they made him teach something). he said,”barba, do you know why i like history? because the dates never change; the people never change, the places never change… you never have to learn anything new”.
