Tick! Tack! is the third visual novel created by Navel for Microsoft Windows. It's the first sequel to Navel's first game, Shuffle!, continuing Nerine's path.
The name is a possible example of Engrish, as the proper English name would be "Tick! Tock!" (i.e. the sound a clock makes). However, certain languages (such as German) spell the sound a clock makes this way, so whether or not it is a mistake is open to interpretation.
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.
an extended description!