Two Defenders (守り守られる者, Defend the Defender in the Japanese Version) is Paralogue 17 of Fire Emblem Fates.
This paralogue is unlocked once Benny has achieved an S-Support with any female character.
The player must rout the enemy without letting the village get captured. If Ignatius survives the chapter, he will join the player's party.
The script for this chapter can be found here.
Subjective: The following part of this article is based upon the editor's personal experiences and opinions, and therefore may not be applicable for all readers.
Your units start at the top of the map, with Ignatius defending a village in the middle right.
There are several Ninjas or Master Ninjas (depending on how far the story has progressed) near Ignatius, and can be very problematic if this paralogue is attempted near endgame. This is because the ninjas have far higher speed then Ignatius and are usually able to kill him quickly. If you attempt this paralogue near endgame, it is advised to pass Wary Fighter and either Aegis or Renewal to give Ignatius more durability, since Shurikenbreaker will not do much given his low speed.
Pass down Benny to Ignatius as quickly as possible, so you can use Ignatius' Offspring Seal (if it is in his inventory) to quickly allow him to get his stats up to catch up with the rest of the units. Have someone ferry him over (and perhaps use a Rescue staff or Azura's singing) to reach him in 1-2 turns. The rest of the enemies can be dealt with normally.