Found the source (I think), seems some time ago Miwa did several fan designs about Volsunga Saga charas and tweet if they should send them to Higashide and Sakurai (Remember that acording to old interviews, Higashide had the idea to split Sigurd and Siegfried into two characters and was who proposed to Sakurai to use Bryn in Fragments, what made Sakurai the final writer then to complete their designs)