what does the OEM JDM cap look like? Mine had a replacement CPC cap that clicked as well but it didnt seal properly, pretty sure it was a replacement for a DA9. besides as you can see in the photo, the rim of the filer neck is actually separate and sealed with some kind of rubber/sealant that was all perished and coming out, you can actually see some of the seal on the flap in photo 2.
I guess my car is no longer fully genuine JDM :(