The present invention provides novel compounds having a P2X3 and/or P2X2/3 receptor antagonistic activity.A compound of Formula (I):wherein Ra and Rb, and Rd and Re are taken together to form oxo or the like; R4a and R4b are hydrogen or the like; n is 1 or the like; R2 is aryl or the like; s and s' is 0 or the like;R9 and R9' are halogen or the like; R20a and R20b are hydrogen, alkyl or the like; u is 1 to 4; R13 is hydrogen or the like,or its pharmaceutically acceptable salt.