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I saw a MAD of Ryosuke Nishii persuming he was responsible for 0:00 - 0:13 part as 1st KA.

On Plurk(a twitter-like site in Taiwan), someone claimed that his friend 伍柏諭(Boyu Wu), a taiwanese animator working in A-1 worked on the cuts where Smile was holding his pants and starting with the serve. He writed Smile but I think actually that may be Peko by mistaken which can mean 0:00 - 0:03 and 0:13 - 0:16.
(for anyone who can read Chinese)

So my guess is 0:00 - 0:03 Boyu Wu, 0:03 - 0:13 Ryosuke Nishii, 0:13 - 0:16 Boyu Wu, 0:16 - 0:21 I have no idea, 0:21 - 0:22 Shinya Ohira. But all cuts have been heavily corrected.

Boyu Wu also worked on AnimatorExpo Me!Me!Me! but I have no idea where he had done.
My full guess goes like this:
0:00 - 0:03 Ryosuke Nishii or Boyu Wu as 1st KA, cleaned by Shinji Hashimoto
0:03 - 0:05 Ryosuke Nishii
0:05 - 0:08 Ryosuke Nishii, cleaned by Shinji Hashimoto
0:08 - 0:13 Ryosuke Nishii
0:13 - 0:16 Boyu Wu, correted by Shinya Ohira
0:16 - 0:21 Boyu Wu but cleaned by Shinji Hashimoto
0:21 - 0:22 Shinya Ohira or someone else but heavily correted by Ohira
0:14 was rotoscoped from the Ping Pong live-action movie. You should ask Yuasa on twitter to confirm the parts.
sakugaku said:
0:14 was rotoscoped from the Ping Pong live-action movie.
Oh wow, great observation. Never noticed this…