Later that same year, Kubo entered the Japan Shogi Association's apprentice school at the rank of 6-kyū under the guidance of Awaji.

[11] The victory made Kubo a "2-crown" (a player who simultaneously holds two major titles) for the first time.

[16] Kubo, however, was unable to defend his title once again the following year when he lost the 68th Ōshō match to Watanabe 4 games to none.

[19][20] Kubo is considered to be one of the foremost specialists in the Ranging Rook opening and has been nicknamed the "Sabaki Artist" (さばきのアーティスト) by fellow professionals for his skill at handling such positions.

He is also known for his ability to persevere in difficult, even disadvantageous, positions and has been nicknamed the "Nebari Artist" (ねばりのアーティスト) as well.

Kubo has received a number awards and honors throughout his career for his accomplishments both on an off the shogi board.