[2] He learned how to play the game from reading books written by Yoshiharu Habu,[3] and as a third-grade elementary school student played his future mentor shogi professional Mamoru Hatakeyama for the first time in an instructional game.

[4] As a fourth-grade student, Saitō personally wrote Hatakeyama asking for formal instruction,[3] and formally entered the Japan Shogi Association's apprentice school at the rank of 6-kyū in September 2004 under the latter's guidance.

[3][5] Saitō steadily progressed as an apprentice professional, reaching 1-dan in November 2006 and entering the 43rd 3-dan League in April 2008;[5][6] his progress, however, slowed and it took him eight seasons of 3-dan League play before he was able to obtain professional status and the rank of 4-dan by winning the 50th 3-dan League with a record of 15 wins and 3 losses in March 2012.

Saitō had defeated Tetsurō Itodani the previous April to earn the right to face Habu,[8] but ended up losing the title match 3 games to 1.

[9] In July 2018, Saitō defeated Akira Watanabe to become the challenger for the 66th Ōza title against Taichi Nakamura.