>>4470740
It's a yuri game where the romantic feelings between two twin sisters are core to the main story.
However talking more about it to people that never played it is, in my opinion, not the best thing as it is a game best enjoyed blind. It is not so unlike Signalis in a sense even if figuring meanings should be obvious in FF2 as it is much more straightforward.

Denying that the feelings between the girl are not romantic between the girl is quite foolish, as the series kept having both incestual themes and romance in every games after 2. Furthermore it also features several lesbian couples and characters.

>>4470749
3 is a sequel that both ties 1 and 2 and confirms that the normal mode ending is canon.