In complete honesty, what kept me reading was the side characters; while none are seen through the manga's entirety, they honestly made me smile.
Overall the main characters felt very lackluster; while there is definitely a story of growth being shown, at no point was I truly invested in it. Even once we began to see the support going both ways. Creating a more healthy relationship between the siblings.
The only point I found myself actually becoming excited was towards the end when a side character reappears and provides support to Kirika.