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Download the user manual here.
There are three major path choices to make during the first generation.
At the beginning of the game, it is necessary to sometimes make choices to take best path even though it might lower the affection of some of the heroines.
During the middle stage of the game rely on "the shortest distance between two points is a straight line," but not too strictly to discover new paths.
For options that appear at the end of the game, it might be better to chose a harder route.
The rule of thumb is to make decisions that raise the affection of the majority of the heroines.
Remember that some decisions should be made without thinking of the affections of others at all.
Also, try not to worry too much over the link gauge. There will be plenty of oportunities to make adjustments later on to view special events.
If the link guage is toward the light and the affection of all the heroines are high at the very end, an event for one of the characters occurs, so try your best to make adjustments.
Since one of the most difficult challenges to face your hero (talking to girls) happens toward the end, make sure to adjust for any shortfalls you may have made during the generation in the link guage or affection levels. Expecially watch the link guage since it can shift dramaticly in some cases.