After Corrin reaches support rank S, you can recruit his/her child, Kana, in this paralogue.
How to Unlock
To unlock this paralogue, Corrin must reach support rank S with a unit of the opposite gender.
Rout the Enemy
You won't be able to talk to Kana to recruit him/her during the battle, but you do have to protect Kana and prevent him/her from being killed during the battle.
There are Dragon Veins in the area that will fill or empty the moats, which will limit the movement of enemies and your units if filled.
Two named enemies, Lloyd and Llewelyn, will appear at turn 8. If you don't defeat them within two turns, reinforcements will start showing up.