« Toys and Merchandise / Unbox Go Nagai Collection

These 'blind box' models went on-sale on July 5th 2020 and came in packs of twelve.
There were 10 main models available, and each box would have one of the 10 models, plus two out of six "chase" versions, which were re-coloured versions of the above.

The marketing material shows six silhouettes of the chase versions, one of which is clearly Dai-X.

This is apparently how there come to be two colour variants of the Dai-X model.

The one with the white mask is the 'normal' version and the one with the yellow mask is the 'chase' version.

It would make sense that the yellow-masked version would be three times more difficult to find, since it would only be included in every third box, unlike the default version.