The basic set-up is that Rin, Nerine, Itsuki, and Mayumi find a strange watch that transports them back in time, where they met Forbesii before he is married and has Nerine. While he is engaged to Ai, his maid, Sage, is also in love with him, causing a love triangle. The players actions determine who Forbesii ultimately ends up with, and thus who is the mother of Nerine.