It's just like others have said. It starts off really well, unbelievably believable. It's about a girl who ends up fooling her younger step brother by wearing a high school uniform. It's actually ridiculous. Her brother falls for her trick and even goes through crazy lengths in order to date her. He doesn't realize it's actually his sister, whom you suspect has feelings for her. This is "Life With Derek" if it actually went the step-sibling route.
But alas, apart from the first couple of volumes that I thought were ridiculous, Ecuador, of all places for example, it morphs into a lackluster shoujo but not quite shoujo as the characters are all in college.
When you get to the ending, my god.
Incredible beginning. But loses its threads. Girl of course ends up in some weird ass love square. How's that believable. Don't get me started on their parents.
For fans of Marmalade Boy. I did think the romance was pretty cute but it lacked believability.