Obtained: Otsuna – Yoshinaka Bay
Speak with Yuna near Otsuna coast
Travel to Yoshinaka Bay to find Yuna near a camp and speak with her.
Follow Yuna
Follow Yuna.
Kill the Mongol
Kill the Mongol near the bonfire.
Go to the Mongol Camp
Follow the path down to the camp.
Defeat the Mongols
Kill the Mongols in the camp.
Go to the row boat
Head to the boat along the coast and hop in.
Defeat the Mongols
Kill all the enemies to complete the tale.