There are only ever three Yuusha's present on the map. In the beginning they are Mimas, Ruidia and Viara. When you have had an encounter with a Yuusha she will disappear from the map temporarily.
If there are less than three Yuusha's on the map, one Yuusha will reappear at random each Yuusha turn. Later on, when you increase your level, Eclair and finally Ennis will appear on the map.
Click on a highlighted field to move there. The yuusha will move when you have moved. Click the current field to skip moving. If you move into an area with yuusha, or a yuusha follows you there on their turn, they will attack.
For each three moves that you make without encountering a yuusha, one of Saga's stats will increase. The three moves do not have to be consecutive, but if Saga orgasms during an H-scene with any yuusha, the counter will be reset.