I just finish reading this manga.
Here the summary of it that I find on mangafox.
Yamato loves his little sister. His sister is the cutest and sweetest girl in the world, and he won't settle for second best. Unfortunately, everyday life and the rest of the world intrude on his idyllic plans, and he finds it's not as simple as he imagines it should be. Follow along with tough Yamato and cute Masaki as they deal with the problems of an otherwise normal family life.
I thought the story was funny and cute. I don't think the storyline isn't bad. I would love to hear you guys opinion on it.