Terahara went on to Nichinan Gakuen High School and participated the 83rd Japanese High School Baseball Championship in the summer of his junior year. In the second round against Tamano Konan High School, he pitched a fastball of 158 km/h, the fastest in high school history. This record is still the fastest record as of 2023.[3]
In 2007 season, Terahara finished the regular season with a 27 Games pitched, a 12–12 Win–loss record, a 3.36 ERA, a 163 strikeouts in 184.2 innings.
In the 2008 season, he pitched as the team's closer, recorded with a 41 Games pitched, a 3–9 Win–loss record, a one hold, a 25 saves, a 3.30 ERA, a 66 strikeouts in 71 innings.[2] And he participated the All-Star Game for the first time in Mazda All-Star Game 2008.[6]
Terahara pitched in 101 games in four seasons with the BayStars, posting a 21–31 win–loss record, a one hold, and a 22 saves.
In 2011 season, Terahara finished the regular season with a 25 Games pitched, a 12–10 Win–loss record, a 3.06 ERA, a 112 strikeouts in 170.1 innings. And he participated the All-Star Game for the second time in Mazda All-Star Game 2011.[8]
In 2012 season, Terahara finished the regular season with a 16 Games pitched, a 6–8 Win–loss record, a 3.92 ERA, a 61 strikeouts in 101 innings.
He decided to exercise his free agent rights during the off-season.[5]
Fukuoka SoftBank Hawks
On December 4, 2012, Terahara signed with the Fukuoka SoftBank Hawks and return to the Hawks for the first time in six seasons.[9]
On April 2, 2014, Terahara achieved his 1,000 innings in a game against the Hokkaido Nippon-Ham Fighters.[10] He was also the winning pitcher in the game against Tohoku Rakuten Golden Eagles on April 16, setting a record for winning against 13 teams, including all 12 NPB teams and the defunct the Osaka Kintetsu Buffaloes.[11]
After returning to the Hawks for six seasons, he was plagued by frequent injuries, including surgery on his right knee, but pitched in 101 games, a 16–17 Win–loss record, a 9 holds, a 186 strikeouts in 286.1 innings.[12]