Complex sentence: While Kaede blushes a bit Rin doesn't take it seriously but more as a joke and is concerned that since Kaede always does things for his sake, most of the other guys have avoided her.
Split into simpler sentences: While Kaede blushes a bit, Rin doesn't take it seriously. He is more concerned that since Kaede always does things for his sake, most of the other guys have avoided her.