To anybody that is struggling to obtain any of the achievements, here are some tips to help you,
Firstly:
Make of the girls max level in all of the stats.
Secondly:
In the perks tab there is an ability that allows you to see achievement items when you use exploratory vision.
(It requires a certain amount of "lust power" to unlock this perk"
Thirdly:
To go to every location in the morning and use exploratory vision, then skip time and use exploratory vision,
repeat until you can no longer be in that area (When it becomes Night), do that for every location, Sometimes it
requires a certain character to not be there so that the achievement item can appear.
Example:
For the "Let The River Flow" achievement,
you need to go to the refuge and go to the bridge in the evening,
If Natsuki is present there the achievement item may not appear and if she
is not there, then the achievement item can spawn (given that the all the required stats are maxed).
It will appear on the left ledge of the bridge.
Also make sure that the Achievement you are looking to unlock is actually enabled
Example:
You must have foot fetish enabled to see the achievement items related to foot fetish to
appear.