Kotegashi (sic!), it seems like vfarias asked for Seagals teachers not his students.
As far as I'm aware he recieved his shodan (black belt) directly from K. Tohei (at that time head instructor at Hombu dojo, Tokyo. He also credit Hiroshi Isoyama (8 dan aikido and direct student of the founder), Seiseki Abe (10 dan aikido and direct aikido student and chaligraphy teacher of/to the founder) and Bansen Tanaka (9 dan aikido and direct student of the founder) as his teachers at various points. His first instructor would be Harry Ishisaka of the Orange County aikikai. There are most likely others but these are the major ones I believe.
/J