this is a no-name chinese branded rear spring. this is one of the odd things about this bike. Typically Japanese brands take great care to use quality parts and in this case a lot of the parts are pricepoint parts. the frame is chinese made, it’s steel (instead of aluminium), the seat is a fake brooks like springer model, the bmx wheels are no-name.
So it’s curious what market they were aiming at with this bike. and maybe that’s why i can’t find anymore info, i guess customers couldn’t figure it out either.