From the pages of Wasyu's Encyclopedia Tenchicca--
Emblem of Power (OVA)
n.: Unlike the cosmetic markings found on many Juraian royalties, the dual-triangular shaped emblem on Sasami's forehead is real. Sasami received this emblem after her assimilation with Tsunami, who owns a similar emblem (a pair of circles as opposed to triangles). The Emblem of Power glows when Sasami accesses Tsunami's power or envisions Tsunami's Dream.