You can't really compare these two because if you try you will not be able to watch the J version.

The story is pretty good but of course a lot of things are left out because the episode count is cut down. They did a good job of including the important scenes. I didn't bother watching the last episode cause I kind of got bored with this drama but I heard the ending is better than the K version.

The cast was great and did the best they could, but I didnt really care about their characters. The entire cast didnt have the same chemistry that the K version did. Still everyone managed to pull off thier parts.

The music in this was just good. I kind of forgot they were playing a band because except for 2 scenes you didnt really see them practice or play anything. Definitely cant compare to the Korean OST.

I'm not sure I'd rewatch this or not just because I could watch the K version.

Overall this isnt bad or amazing its average. I'd recommend watching the Korean version if you find the summary interesting.