Yoshimura Kenichi is a Japanese actor who has lived in Korea for 10 years, teaching Japanese to Korean top stars. He talked about some of his students, including SeungGi, in a recent interview:
Lee Seung Gi sshi is also a very smart actor. I heard that at the peak of his study, he studied Japanese for more than 8 hours a day. I remember him as an exceptional actor who improved his Japanese so much that he could converse freely only a few months after he began studying in earnest.
source: newdaily via nate
English translation: tryp96.wordpress.com