Iroha is understandably worried about Mashiro, but the very fact that Mashiro is not only a cousin, but also a childhood friend to Akiteru means Mashiro's most likely the losing heroine here.
Let's not mention how Iroha is the titular girl and plastered all over the covers. It's not impossible, but making her lose is sure to cause "bait-and-switch" backlash from readers.