These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
The people from Lacryma's future don't all come from the same present, but didn't hop realities or anything to get there.
Dimensional convergence. It was happening to both Shangri-La and La'Cryma. Therefore multiple pasts end up crossing into the same future.
Midway through the series Karasu becomes concerned that the other future has broken causality and now the future might be able to influence present events. Despite Karasu himself being from the future and having influenced the present plenty from the very beginning of the series.
Fridge Brilliance: The story isn't about Haruka at all. It's about Yuu deciding who he wants to be.
Fridge Logic: There are an infinite number of dimensions which are produced from every possibility in every moment in time. Central to the plot is a future event in another dimension which will destroy all dimensions in the multiverse. Shouldn't the universe have already ceased to exist? note To prevent Natter from reaching critical mass, go to the Discussion Page for more detail.