Since it's your first map I'm gonna just give you some broad suggestions, maybe you could take away some concepts that's helpful to you from my ramblings~
00:11:139 (3,4) - switch, snares are on the white line and the bass drum's on the red, not the other way around
00:13:539 (15,16) - ^
00:15:939 (29,30) - ^
00:18:339 (43,44) - ^
Think about structure more; for instance let's look at the structure of this section from 00:10:839 to 00:20:439 at the beginning; the whole bit consists of 8 bars, which can be divided into 4 2-bar phrases, and phrase 1 and 3 are similar. So what you could do is to use similar patterns for phrases 1 and 3. E.g. 00:11:589 (5,6,7,8) - dkdk, so 00:16:389 - can be dkdk too. Thinking about stuff like this can make your mapping more internally consistent.
Strategic pauses can be used to accentuate notes both before and after the pause (but personally I think pauses emphasize notes before them waaaay better than notes after). E.g. at on onbeat like, 00:15:639, where there's a heavy piano chord, you could delete 00:15:789 (28) to further emphasize the onbeat. Actually just think about emphasis more.
Speaking of emphasis, k's usually emphasize sound in the music more than d's. It's important to consider where in a pattern you should use k's, it's equivalent to considering which note in a pattern you want to emphasize. E.g. 00:47:889 (183), if this is a d instead of a k, the kkk triplet after would be much more noticeable. The k's can then also represent the entry of the piano this way.
00:20:139 - this clap sound in the music deserves a note imo, not just sliderend-ed. Perhaps change the slider to a spinner and add a K here.
It's helpful to listen to the music at 50% playback, you'll notice some notes are out of place if you want to match the music better. E.g. 00:23:439 (65) should be moved 1/2 forward to 00:23:589; and 00:24:039 (67) should be moved 1/2 backward to 00:23:889.
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Sometimes it's confusing when you map to sounds that's not actually on the beat where you've placed the note; e.g. 00:30:639 (101) should actually be on the blue tick just before it, at 00:30:564. I can understand why you did that, if you did place that note on the blue tick the rhythm would be too hard for muzu players (or perhaps you just misheard the position of the note, that's ok it happens to everyone), BUT when you put the note as is now players will get confused, because the snare sound in the music you're mapping to and the hitsound of that k would occur at different times. This happens A LOT in this muzu, the drum pattern is really intense and complicated and can't be represented thoroughly with muzu level of density and muzu patternings, which is why people ask you to map Oni and Inner Oni
A solution to this problem is to just delete the note. Just delete 00:30:639 (101). That music/hitsound conflict wouldn't happen if there's no note there, would it?
Another solution is to delete the note AND think of another way to represent that part of the music. In this case, delete 00:30:639 (101) and add a d at 00:30:489 perhaps.
Please be reminded that this really happens A LOT in this muzu. A LOT. Too many to count. Do consider fixing them. (remember to use 50% playback rate to listen carefully to note timings)
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When doing build-ups towards a big note, using notes of an opposite color before that D or K is a common way of making that build up sound more intense.
E.g. 00:38:439 - I would do it like this:
E.g. 00:57:639 - I would do it like this (a bit too hard for muzu, but this is just so you can get the idea):
Using k's more and more before the D is also a good way to do build-ups.
Random suggestion: at 01:39:639 you can hear the melodic synth at regular 3/2 intervals, if you want to map those in consider this:
76 and 82 are big notes.
Don't be scared of using 1/4s in a muzu btw, your kiai time has very few of those and it's supposedly the most intense part of the song. I think putting more triplets in while still keeping the SR below 3.5 is a good starting point, just make sure not to use consecutive triplets.
00:10:239 and 01:40:989 and 02:34:333 - adding a spinner or slider at these places could be a nice effect. Up to you though.
Oh and also... I usually use claps instead of whistles as my k, so... there's that