[2] In 1999, Yoshihara was loaned to Albirex Niigata, a J2 League club, where he was called to the starting lineup in the season-opening match.
After Yoshihara returned to Yokohama F. Marinos in 2001, he made a permanent move to Kawasaki Frontale in midseason where he became the regular goalkeeper in 2003.
[3][2] The following year, he maintained a record of seven consecutive scoreless matches which greatly contributed to Kawasaki Frontale's promotion to J1 League, during which he established his position as an indispensable goalkeeper for the team.
In 2005, an injury prevented him from being called to the starting lineup in the season-opening match, yet he made his appearance from the game against Tokyo Verdy on and contributed to stopping the team from repetitive defeats.
However, at the end of 2006, during which Kawasaki Frontale was in close proximity to winning the championship, Yoshihara secured his primary position once again in the match against Sanfrecce Hiroshima.
His position as the regular goalkeeper seemed promising, yet, Yoshihara was injured during a match against Sagan Tosu on July 1 in the 25th section, damaging his left knee posterior cruciate ligament.