To Obtain Fenrich's Epilogue you must:
1) Complete the first 9 episodes
2) In Episode 10 Complete Stages 1-6. DO NOT COMPLETE 10-7 which is the final stage
3) If you haven't done so already, call a Senate and unlock the "Legendary Tree" Evil Symbol and place it somewhere on the map in Cam-pain so all squares are visible. The Pattern is +.
4) Go back to Base and Save your game. You have multiple slots so what I did was save the game in slots 1-5. Only one epilogue can be unlocked perm playthrough which is why we use multiple saves
5) Go back to the Cam-Pain
6) Place Valvatorez on the L square and Fenrich on the one of the other 2 squares. The middle DOES NOT count.
7) Hit LT or whatever button it is to "Dispatch an evil deputy" and walk up to the Legendary Tree and hit the Action button to interact. Set Fenrich to "Comrade"
8) Go back to the Base and Save your game to one of the 5 Slots you saved Earlier but ONLY ONE. (You can also change your save icon in settings to the character you doing the Epilogue for in Settings to make it easier to identify saves)
9) At this point Quit and load up one of the other saves and repeat steps 5-8 for each character. So once you are done, you will have 5 Saves with all 5 characters set up at the Legendary Tree. Skip if Completed already through one of my other Epilogue Guides
10) Now each character has a specific requirement to unlock an event needed to get the epilogue. Check each characters achievement for their individual task. Fenrich's is to have Valvatorez use 10 Team Attacks with him. To complete a team attack you must attack with another character in an adjacent square. I dont know if it matters whether Fenrich or Valvatorez are the original attacker however I did this with Fenrich initiating the attack.
11) Load up any level and use both Valvatorez and Fenrich to complete 10 team attacks. This will likely require you to launch the stage a few times. It does not need to be all in the same stage.
12) Once you used 10 team attacks, finish the Stage and go back to Cam-Pain. You should get a prompt that an event has occurred under the Tree. Click through the prompts to go through the scenes
14) Now Complete 10-7 and you should unlock the Epilogue after the Credits.
15) You will be prompted to Save after the Epilogue. You can choose to do so if you wish. Obviously only save to the dedicated save for that character if you do.