Changed offset to 3
BPM has been changed to 100 with 2/4 time to emulate 6/8 time.
HP and OD values changed to your suggestion
Added hit-normal
Changed song title to "Street Piano"
Added tags, but removed "easteregg" because I don't think that's necessary.
Also fixed a typo in your tags - it is "그란디스", not "그란시스" (gransis lol).
The reason why the strings were represented in the earlier sections and not the later ones is because the piano does not have as much impact in the earlier sections. The later parts of the music has the piano become more impactful, so I shift the focus more onto the piano by adding more notes to follow the streams/chords, and taking away notes that represent the strings. This makes the piano feel more emphasised toward the end during play.
refer - 2099450#4078841/10979664
However, kept the anchors the same instead of following the pitch on the note before the new bar to make it easier to read and play as it's not the top difficulty of the mapset.