In Valkyria Chronicles II for the PSP, you can unlock Isara Gunther from the original Valkyria Chronicles.
You’ll need to copy a Valkyria Chronicles I save file from you PS3 to your PSP. Once it’s copied, go to Extras in Valkyria Chronicles II and load that saved file. This will unlock Isara Gunther, and Isara’s Dream sticker for your tank.