Resinya! (レジーニャ!) is Cospa brand which includes both dolls and figures. We're interested in dolls, of course, so we should start with Resinya! Portrait Collection.
Cospa already had C-Zone doll and doll clothes line in collaboration with Azone when in 2008 they decided to launch their own original concept. Resinya! Portrait Collection initially featured Da Capo characters and offered only busts instead of full dolls.
These could be displayed as PVC prepainted figures but were actually intended to be compatible with Obitsu bodies. The head is installed on a default 27cm or 25cm body:
By that time Cospa had had an experience in making clothes for Obitsu, so Resinya! Portrait Collection busts soon were available with Starter Sets:
The clothes sets were also sold separately under the name of Mini Costume Collection. Now they are also available for 23cm Obitsu bodies, because...
...year 2011 saw the arrival of "fully-bodied" dolls sold as Cute-rate 23 line. They use 23cm Obitsu bodies and represent K-On! characters. It is not clear whether Cospa is planning to expand the line.
Resinya! website is here.