Koroki knocked in a rebound from close range to open the scoring in the sixth minute.
Fellow forward Yuzo Tashiro added another in the 64th minute when his shot from Yasushi Endo's cross flew over goalkeeper Yoshikatsu Kawaguchi.
"We were two forwards today with Yuzo. Previously we couldn't score, so I really wanted to score with him today. The ball came to me and I just hit the ball," said Koroki. "I'm glad, because I really wanted to score today."
Kashiwa keep top spot
Kashiwa Reysol kept their spot at the top of the standings with 25 points, after their 2-0 win over bottom-placed Avispa Fukuoka.
They are followed by Vegalta Sendai on 21 points, Kawasaki Frontale on 20, Sanfrecce Hiroshima on 19 and Yokohama F Marinos with 18.
Sendai, also hit by the quake and the tsunami it triggered, remain unbeaten this season in 11 games as Naoki Sugai struck home an equaliser five minutes into injury time, to ensure his side drew with Albirex Niigata 1-1.
Kawasaki defeated Hiroshima 2-0 with goals from Takuro Yajima and Kosuke Kikuchi, while Yokohama crashed to a 2-1 loss to Gamba Osaka.
In other games, defending champions Nagoya Grampus suffered a goal in injury time to be held 2-2 by Omiya Ardija, while Cerezo Osaka whitewashed Ventforet Kofu 2-0.
Montedio Yamagata defeated Vissel Kobe 2-0, and Shimizu S-Pulse downed Urawa Red Diamonds 3-1.