I'm at a loss here as to how to unlock these "dream invasions". I'm playing mostly by trial and error and I've reached a point where I've unlocked a good deal of the abilities but nothing seems to relate to dreams in any way... Could someone please give me some pointers?
The girls that have dreams and their locations are:
Yuu (Glasses) - Flower Path
Nanase (Umbrella) - Guest House
Ako (Bugcatcher) - Guest House
Kokoro (Heart/Maid) - Guest House
Amy (Blonde) - Guest House
March (Younger Sis) - Shrine (not the one the player sleeps at)
Uta (Tomboy) - Corner of the Village (Go right from the busstop)
Hime (Princess) - Tunnel
These 8 dreams being discovered and entered are also the condition for the skill 生暖かい風 (warm breeze) to reach the next tier.
Special mentions
Nanase is unique in the sense that she behaves differently in the 2 types of runs. The version that she's walking around, her dream is not available. And the one that her dream is available at the guesthouse, she will not be walking around. Just in case you're wondering why you can't see her dream. Why this happens is story related so I won't spoil further but you can see my other posts for what to do.
Hime and March also don't appear in 1 of the 2 types of runs. And obviously if they aren't there their dreams won't be too.
Fox also has something like dream bubbles, but since it's different she doesn't count as one of the 8. Her original bubble appears only in 1 type of the 2 possible runs, and she'll appear at night 1 tile before the sleep shrine. After that her bubbles will show up in the forest, keep in mind that if you pursue this, you will be locked into an outcome where the game clock disappears, and your only options are to fight her and end the run, or go to the sleep shrine and end the run.