Given the task definition and input, reply with output. In this task, you will be given a passage to read. A fill in the blank question will be given to you. Your answer should fit the blank appropriately.

Kurt and Riela were featured in the Nintendo 3DS crossover Project X Zone , representing the Valkyria series . Media.Vision would return to the series to develop Valkyria : Azure Revolution , with Ozawa returning as director . Azure Revolution is a role @-@ playing video game for the PlayStation 4 that forms the beginning of a new series within the Valkyria franchise . fill in the blank :Kurt and Riela were featured in the Nintendo 3DS crossover Project X Zone , representing the Valkyria __________________ .
series