QA hBP01-096〈Usada Pekora〉 with no fans attached was chosen for the ability of the bloom effect "Let's Make this the Best Concert Ever!" of hBP03-012〈Himemori Luna〉.
If I attach hBP01-123〈Wild Rabbit Alliance〉 to hBP01-096〈Usada Pekora〉 and use Arts, does the Arts get +20?

ANo, as that holomem did not have a fan attached when it was chosen for the ability of the bloom effect, it does not get +20.