good question...
Me thinks that if
Reimu is Mario
Marisa is Luigi
then
Reimu's opposite, Sanae is Wario (another shrine maiden)
Marisa's opposite, Alice is Waluigi (another witch)
I think alice because of IN...their personalities are totally opposite. one wants to solve the moon incident and the other didn't care. straight-forward, another indirect.
That's my guess. other wise i'd say for reimu...maybe yukari and then marisa.....i dunno ._. shikieiki? bleh.