When Jun Shirasaki was a young boy a new family moved in next door, this included twin girls Naori and Rumi. Naori, much like Jun, is bookish while Rumi is sporty but a bit of a loner. The years pass and they remain friends. Somewhat inevitably they develop feelings for each other; this leads to some awkwardness as nobody wants to hurt others' feelings or damage their friendship.
This is a cute enough romance anime. It manages to avoid some of the more obvious genre clichés and there is no obvious answer as to who, if either of the twins, Jun should end up with. The twins are not identical so we don't get the stale cliché of them being mistaken for each other. The animation and character designs are good. Overall I'd recommend it to fans of romantic anime but wouldn't say it is a must watch; the sort of show one enjoys while watching then forgets about.
These comments are based on watching the series in Japanese with English subtitles.