Sega has just announced Valkyria Chronicles 3 collaboration with Infinity. When Valkyria Chronicles 3 locates a save file from Phantasy Star Portable 2 Infinity, Nagisa will become available in that game.
This save data unlocks a mission called "リトルウィングからの挑戦状∞" or known as "Infinity challenge from Little Wing." In addition a Rapico sticker can be obtained via inputting a password.
If you obliterate an "ace enemy" who appears at the end of the mission, you can receive Nagisa's signature sword, the Steel Hearts! In addition when you clear the mission you can get a red ribbon.
Rapico sticker is obtainable by inputting this password. You can place this sticker on your tank:
R72ZPF4L7L3C7G6M
[via 4gamer]