The user jes wrote that this series is a mix of "A Love So Beautiful" and "When We Were Young". I would somewhat disagree; it's much, much closer to the latter (it could be even called a 'remake' or 'another adaptation'). There is romance, but it's not the main focus of the series. Just an Encore is primarily about growing up, the last year(s) of high school before university, and all the experiences, dreams and conflicts which come at that age and point of life. I can only repeat again that it is very similar to "When We Were Young"; the main differences being time setting (this one happens around the year of 2005, so about decade latter than WWWY) and ending - where WWWY closed with high school graduation, "Just an Encore" adds a final '9 years later' conclusion.
To sum it up: if you are looking primarily for romance, similar to "A Love So Beautiful", you may end up (slightly) disappointed here. However, if you are a fan of WWWY, then this series is pretty much a must for you.