Title says it all I guess.
I mean afaik that song is in the JP version called "Readoro KOI KOI" something. https://phantasystar.fandom.com/wiki/Phantasy_Star_Online_2_The_Animation_Readoro☆KOI☆KOI!_One_More!
Considering most of the other songs from the live concert you can get, like those persona songs (Rivers in the Desert remix) etc. Knowing this is an old game even tho it just hit Steam/EU on 5th of August so I do understand somewhat why something new won't be added, but still, it would be strange if this was impossible to add.
Like the audio is literally already in the game, during the live concert.
If this topic has already been asked and even adressed I apologize and send me a link to it.
Thanks for reading!