There is no official version of Attack on Titan 2 for the PSP or PPSSPP emulator. While a sequel to the 2016 game exists, it was released for modern platforms like Nintendo ($39.99), PlayStation 4 ($39.99), and Steam.

• Common File Name: Often named Attack on Titan.iso or the Japanese title Shingeki no Kyojin.iso.
• Region: Look for the "English Patched" version if you cannot read Japanese. While the game was originally Japan-only for PSP, fan translations are widely available.

Conclusion

While Attack on Titan 2 was not originally released for the PSP, a PS3 version of the game was released in Japan, which was later ported to the PSP. However, the PSP version was only released in Japan, and it seems that the game was not localized for Western audiences.