You have never seen entire Kosen event live, let alone competing in it or even read the rule set.
You are talking to a guy, who medalled several times in Kosen tournaments, has direct connection and personal friendship with the only group in Japan, organizing such events and preserving the tradition, and you have the nerve
You are a flaming example of what I wrote above, regarding people in desperate need of myths.
Here, let me break it down to ya:
Currently, about %40 of the competitors in Kosen tournaments are BJJ players.
Kosen events are team tournaments.
I have been part of several teams: Suita BJJ, Daishin Judo Club and my own team Yagadome.
To participate in Kosen events, one must be a part of a team.
Each team can bring as many competitors they want.
When going against another team, each team presents 5 players.
So, good strategy is to bring 8-10 players to the competition and always keep a few guys fresh, to go against the next team (you can replace players and order of their appearance).
The big and experienced competitors are strategically placed at 4th and 5th spot.
The team that has more wins is declared a winner and proceeds into the tournament.
*Yes, this is where Quintet got the idea from.
Yes, some people do pull guard. Mostly the pure BJJ players, because a lot of BJJ guys in Japan are also Judo BB (Shinya Aoki is not only a Judo and BJJ BB, but also a Sambo national champ and I personally know more than 10 guys like this).
Why it is not a viable strategy to pull guard?
1. Rules.
Judo ground work happens only when both players are in ground position.
Meaning, if you pull guard and the other guy is standing, ref will stop the match and restart from standing position.
So, if the opponent is not willing to go to the ground or disengages, match is stopped and both competitors start from standing.
2. There is no time.
The Kosen matches time vary from 3 to 5 min, depending on the age of the competitors and the tine is agreed between both competitors before the match. Usually,
older guys want shorter matches, because of age and...smoking

(about %70 of the old school Judo guys also smoke a pack a day).
So, pulling guard and shooting for a sub or reversal and pin/sub (its Judo rules: sweeps and reversal dont count for shit) in under 3 min is not a sound strategy.
So, thats that, regarding guard pulling.
As for lineage, let me tell you what the Judo world is in Japan:
The only teams that go back are the university teams.
Simply, because they are institutions and not a family dojos. Meaning, they will have subsidies, constant flow of fresh prospects, who will represent the university in all events, bring back medals and one day will become coaches, if they want.
Similar to wrestling in USA.
The big dogs are:
- Kokushikan university, famous for the most hardcore competitors (both Judo and Wrestling).
My daughter was training wrestling there.
Ishii went to Kokushikan HS and Uni, even if he is from Osaka (his father, a good friend of mine and a great Judo coach, made him go to Kokushikan).
- Tokyo university, where a lot of the national team players came from.
- Ryotokuji university, where currently my friend Daniel Dichev (BUL) is working in the Judo department and prepares for the Olympics next year.
Now, the only Kosen related team is the Kyoto university and they are not top ranked.
I have trained with those guys, I have competed against those guys, I have drank beers afterwards and Im friend with a lot of them, including their coach.
There is no lineage of Kosen.
There is a tradition, specific for Kansai region, where I use to live, that is kept alive and thats it.
You can believe whatever fairytale you want and pray to mythical creatures.
I dont care