Please read the Description!

This secret reveals a very hidden dialog that will not appear during your first playthrough of the game. In order to get both Soren and Pelleas good ending. You must do the following action:

1) Soren and Ike support conversation must be A
2) Part III Chapter 7; have Soren attack Micaiah
3) Part III Chapter 13; Pelleas must survive
4) Part III Endgame; have Soren attack Pelleas or have Soren get attack by Pelleas
5) Part IV Chapter 5; have Pelleas attack Izuka.
6) And you must use Soren during Part IV Endgame.

During the Epilogue you'll find out that Soren is the real son of Lady Almedha.