[Kiwami]

Vinyl figures I assume. They're cheap yet sturdy figures for kids to play with and they're almost always integrated into the DX toys. Hell, for quite some time the vinyl figures actually were the gimmick, they used them in the shows as "Spark Dolls".

And even when the gimmick changed to cards they had that cross sell going on where the vinyl figures came with their respective cards you could use with the DX toys.

I don’t know what sells better, the DX roleplaying stuff or the vinyl figures, but I do think these figures are kind of unique to Ultraman, since even though Kamen Rider and Sentai do have them as well they only do them for main characters, and the figures are not really integrated into the rest of the toy lines.