This is your pretty stereotypical romance that doesn't progress much. They both still love each other, but they both kind of refuse to admit it. They kiss at one point, and then pretend it never happened. The main "conflict??" Is the guy is in love with the middle school version of the girl, and the girl wants him to fall for the high school version.
It is ongoing, and I can't give many specific details because I only skimmed a machine translation version about 6 months ago. If there are more recent developments I wouldn't know. Part of it, is whether or not they wish to date again, they are now stuck together for life as syblings regardless.