Reimu is implying she knows/understands Rinnosuke better, giving her some sort of a lead over Marisa.
Rinnosuke-san, are you here?You're not Rinnosuke-san, right?You're way too invigorated.Caught already, huh... and I was thinking I'd scare you while tending the store...Sheesh, tricked like that...Hey, Kourin! I came to play!I found a rare mushroom, so I'll go ahead and make a stew!Huh?For your information, that person is not Rinnosuke-san.Ooh, Reimu, welcome!Ta-daa!I figured it out right away, though.
