Ancient Training Ground/Forgotten Ruins
Go to the east and enter the portal. In Forgotten Ruings go to east and enter the portal to southeast.
Windswept Valley/Ancient Plaza
Destroy Assaults (better version) and go to east. In Ancient Plaza area destroy another group of them. Go northeast.
Lapis Ruins/W. Valley/Ruined Church/Lost Forest
In Ruined Church take Combat Adjudicator test and enter the forest using door under the stairs. Make your way through the forest: forward, back, right, right.
Echidna could a little harder to beat than before because you don't have Snatch this time. Use Swordmaster style and feed her with long combinations of attacks. Stay close to her.