身内とはいえ9段の方に転がされるのが羨ましい

If you look closely, it is a good "小内刈り” To understand this, the blue player did a “出足払い” on the opponent's right foot. However, the blue player's "出足払い" was incomplete and had no effect. 　As a result, the white player was in a no-damage condition that did not lose his balance, so he made a "小内刈り" using his opponent's mistake. And I got "技あり"

white to blue. Also, unlike what inyu said, white did not capitalize on his opponent's mistake. They both started their idea at the same time (watch in slow motion). There is simply no way human reaction time is fast enough for that to be a reaction. White went for kouchi at the same time blue went for ashi barai. White got lucky because of the way the techniques interacted with each other the kouchi became super effective