I asked Seiko how their Seichu straps worked because I found them baffling.

The keeper where you would usually tuck the material is thin, so you cant tuck the tail in so to speak, while the keeper below it is wider which is a bit counterintuitive.
They cant be worn in the same way as a normal NATO.

This is how they work -

The top keeper is thin and fixed.
The lower keeper is wider and moveable.

Hope this helps if anyone else has one.