The manga is very high quality all around. The art may be simple, but it has character and is quite attractive, too. I think I won't forget this style for a long time, it's probably even going to affect my own drawing style a bit.
The story is very nice too, it's not typical, but still "normal" enough to easily identify yourself and your life with it. It has depth without being complicated or hard to understand, yet it can very easily convey complicated situations and emotions.
Now, as for the slightly weird ending, here is my opinion. Don't read if you don't want to know the ending before having read it yourself:
The daughter role falls in love with the father/guardian role. Quite complicated there and the manga shows that very well.
Right up to the last chapter. That one is kind of a flop, there should've been another volume in between, showing how the father role works out his own stance and evolves it over the two years.
What really made the ending acceptable for me though, was the fact that the author treated the whole situation very carefully and with respect, that is to say, no smut or anything else that one might perceive as not as innocent and pure as the rest of the manga. It wasn't just a way to increase sales, so to say.
The ending was hurried for what ever reasons, but I could still feel the wish to make the ending enjoyable, and not just because it has the face of a scandal. It's not as simple as calling it a scandal and being unhappy with the ending, it's a very complicated situation that has taken years to grow and the manga really shows that. That's the reason I can accept the ending without any complaints except one: It's a bit too early, some more development right in front of the last chapter would've been good, so that we can understand just how Daikichi overcame his "moral horror" and why we arrived where we did.
That's the biggest minus in the whole story, the reason I'm going to give this manga an 8 out of 10, instead of full marks as the rest of the story deserves. We don't really know how Daikichi comes to his decision. "It's impossible for me to refuse Rin[...]" isn't enough, it just isn't. That's not what a (surrogate) father would say, so we need to know how he arrived there from his position as a father.
Now, I'm quite damn tired since I read the manga in one go and I suppose it shows in the wall of text, but I definitely had to write down my thoughts before going to sleep, as I wouldn't be able to do so accurately tomorrow after dreaming about it. I'll go over it once I'm rested. ~ Edited it a bit now. I hope you can understand what I'm talking about. 😀