Some soundtracks from a mobile game, Blue Archive.
Instructions: Extract the folder to assets > mod_overrides, just like what you do to other custom menu OST.
Soundtracks included:
Constant Moderato https://www.youtube.com/watch?v=p7ZRQ0BxtMM
Luminous Memory https://www.youtube.com/watch?v=eM01nJ_lbEo
Lovely Picnic https://www.youtube.com/watch?v=pRdhcgmbUag
Connected Sky https://www.youtube.com/watch?v=7c8p0pRxZHM
Step by Step https://www.youtube.com/watch?v=-8RciEs-ze8
Irasshaimase https://www.youtube.com/watch?v=8CCLQHzywio
Credit: Lloyd Dunamis (https://www.youtube.com/c/LloydDunamis) for providing the files.
For other Blue Archive menu soundtracks, please check this mod by Izanagi: https://modworkshop.net/mod/33940
