[General]
I feel like Normal is a bit too hard for the easiest difficulty.
If possible, could you reduce the SB images to 800x600 or smaller? Generally that's the size limit.
White notes + kiai = pain.
Consider adding jpop as 1 word in the tags.
Timing feels 20ms early or so, try 472?
Lots of unused timing sections lying around, try tidying those up.
[Normal]
00:09:804 (5) - Awkwardly placed repeat.
00:38:040 (4) - ^
00:39:628 (1) - End 1/2 sooner?
01:03:099 (6) - Extend by 1/4?
02:39:648 - Consider mapping this break; ending a break with a spinner...right into another break feels a bit weird..
The rhythms on this difficulty really stood out for me, they were very cool.
[Hard]
00:46:157 (4) - Felt a bit out of place, a note on the white tick before it would be cool too.
02:39:628 - Same thing here as on Normal.
02:54:804 (1) - Not the best place for a spinner, imo.
Neat too.
[Insane]
Wow, high max score. It's pretty difficult though, so I guess it's okay.
Overall, it's pretty good. Feels overmapped in many places though.
Star~