Just input the code's in the 2nd option of Extra mode.

Code	Effect
STMNS3MKZ4NMKT6K	7th Platoons Idol Sticker
9A5MYSG56K47GE3B	BLiTZ Logo
KRSNSNGJTWTYMNRK	End of eternity
YJG6LMRQT9EP5CFN	Gallia Volunteer Sticker
RG7CSKXAGJTWYM96	Saturn Logo
364BNZ29ARL78XCJ	Sega Logo
SGEATFRTWYKCFSXQ	Uzumaki Logo