I mean, when someone close to u never notice u in that way it can be because they're too used to ur presence but also that they just arent attracted to u at all. The way it ended, Suzu, after the movie could just as easily say she only sees her as a sister after all. Tbh, i was expecting that Suzu actually liked Kasumi but since they were like sisters she gave up and was looking for distractions mostly after being apart. That way the ending would be a lil more promissing.