This is a classic shoujo. Yoshizumi Wataru has great craftsmanship, does all the little things right, so her stuff keeps you reading and invested even if nothing particularly unusual is going on. More than the sum of its parts.
It is actually pretty sweet and I found myself rooting for them. It was cute, not overly tragic and little silly. I like it and the FL has a very likable and realistic character which was refreshing. The ML inst a total jerk either which seems to happen a lot in shoujos and there is no concerning "red flag" behavior often found in shoujos. Time flows realistically and I am very glad I took the time to read this.
It is well written as well and the pacing is pretty good.
There was not a single character I disliked and not a single thing I disliked or felt concerned over.
If you are concerned about incest
It is not really incest and they meet each other very late on in life. While I personally find step family relationships odd and they usually make me uncomfortable, this manga some how made it not weird and there was no discomfort reading it.
What I find most impressive is that the anime actually continues until the end of the manga... instead of stopping after 12 or so episodes which is the norm...
The fact that originally all the characters had to be the opposite sex stuck in my head ... maybe it would have been a little different from typical shojo