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Masayuki SATO (31 staff credits for various animation tasks) appears to be three persons:

佐藤誠之 SATOU Masayuki? (In-Betweener; 8 readings including "Masayuki" but the only person at ANN with these kanji is a "Shigeyuki")
He apparently is Shigeyuki SATO, 1 credit in 2008 for Planning Assistance, source: "DVD"; I added another In-Betweener credit for him in a Crayon Shin-chan movie).
佐藤誠之 (2003) ATASHIn'CHI (movie) : In-Between Animation (Studio Jungle Gym)
This is just one wrong credit (which I flagged & added, the wrong entry for Masayuki should be deleted).

佐藤正行 SATOU Masayuki (Background Artist, 4 readings, ANN has 6 persons with these kanji all of whom are "Masayuki", Allcinema gives 佐藤正行 = さとうまさゆき = SATOU Masayuki plus three animes from 2002-2003 none of which he is credited for at ANN)
佐藤正行 (1992) Space Oz no Bouken (TV) : Background - source is gone, additional kanji source
----------- (1996) You're Under Arrest (TV) : Background - "DVD credits"
佐藤正行 (1999) Yu-Gi-Oh! (movie) : Background Art
----------- (2000) Hand Maid May (TV) : Background - "DVD credits"
佐藤正行 (2004) Soreike! Anpanman: Yumeneko no Kuni no Nyanii (movie) : Finish Animation (Hadashi Pro)
佐藤正行 (2005) Lamune (TV) : 背景 = background
This might become a new person to be created.

佐藤雅将 SATOU Masayuki (Animator/Director, "Masayuki" is the only valid reading)
佐藤雅将 (1997) Neon Genesis Evangelion: The End of Evangelion (movie) : Original Picture
佐藤雅将 (1998) Queen Emeraldas (OAV) : Key Animation (Studio Cockpit - Ep. 2)
----------- (1999) Pokemon 2000 - The Movie : Key Animation - "DVD credits"
----------- (1999) Street Fighter Alpha (movie) : Key Animation - no source
佐藤雅将 (2000) Pokemon 3 - The Movie : Animation Director
----------- (2001) Baki the Grappler (TV) : Animation Director - "DVD credits"
佐藤雅将 (2001) Cowboy Bebop: The Movie : Key Animation
----------- (2001) Grappler Baki Maximum Tournament (TV) : Animation Director - "DVD credits"
----------- (2002) SaiKano (TV) : Chief Animation Director - no source
佐藤雅将 (2003) Ashita no Nadja (TV) : Animation Director
----------- (2004) Otogi Zoshi (TV) : Animation Supervisor - source is gone
----------- (2005) Eureka Seven (TV) : Key Animation - "episode credits"
佐藤雅将 (2005) Gallery Fake (TV) : Key Animation
佐藤雅将 (2005) Karas (OAV) : Key Animation (ep 6)
佐藤雅将 (2005) Konjiki no Gash Bell!! (movie 2) : Key Animation
----------- (2005) Mushi-Shi (TV) : Animation Director - "TV credits"
----------- (2005) Paradise Kiss (TV) : Key Animation - "TV credits"
----------- (2005) Xenosaga: The Animation (TV) : Animation Director - source is gone
佐藤雅将 (2006) Air Gear (TV) : Character Design, Animation Director (kanji separated by whitespace)
佐藤雅将 (2006) Death Note (TV) : Key Animation
----------- (2006) Jyu Oh Sei (TV) : Key Animation - "TV credits"
佐藤雅将 (2006) Shin Kyuuseishu Densetsu Hokuto no Ken: Toki-den (OAV) : Key Animation
----------- (2009) Afro Samurai: Resurrection (movie) : Key Animation - "English DVD credits"
----------- (2009) One Piece Film Strong World (movie 10) : Animation Director - source leads to search form
This is the person with the kanji name known to ANN.

Lines beginning with kanji indicate credit entries where either the source at ANN or an additional source in this posting validates these kanji; lines beginning with "-----------" would require a better source in order to be sure. Google didn't give me usable sources for the two remaining background roles; I didn't search for the remaining animator roles yet (as they're most likely staying at their current place anyway).