BlazBlue: Cross Tag Battle Special Edition

This achievement will become available once you've completed the cooperative ending in the blazblue episode. To unlock the cooperative ending you must complete all 3 of the endings for the blazblue episode as well as completing the other 3 stories. Once this is complete you must select the following options during your playthrough of the blazblue episode:

When talking to Gordeau select to Trust Rachel

After fight with Ruby select the Something Fishy option

After fight teamed with Chie select the Help Me Out option

When asked by Nu who you were looking for select either Noel or her (don't pick rachel).

Later when fighting Hyde and Linne select the Accept Help option

Finally don't trust Hazama near the end.

Then from the hub open the menu with and scroll down to gallery mode. Tab to the movie page and click on the credits. You can then immediately exit with the button and the achievement will still unlock.