Highlights:
Towa steps away for a moment after watching over Setsuna sleeping. Just as she does, ninja kidnap Setsuna and bring her to Princess Aiya.
When Setsuna wakes up, she finds herself in make-up and fancy clothing. Princess Aiya gives Setsuna a sob story and begs to have some freedom for just one day. Since the new instructor has never met the Princess and Setsuna is about the same height and age, she would make the perfect substitute.
A little later, the instructor walks in. Imagine Setsuna's surprise when it turns out to be Hisui. Seems Kin'u, Hisui's older sister, duped her younger brother the same as the Princess duped Setsuna. Kin'u was to be the instructor and was paid handsomely for it. She convinced Hisui that she was too busy to do it.
Elsewhere, Princess Aiya orders her servants to take her to the harbor. She heard rumors that something was out there and was dying to see it. As it turns out, it is the large octopus demon, Takonyudo, and it captures the princess.
Hisui replaces himself with a mannequin and tells Setsuna to keep pretending to be Princess Aiya while he goes off to rescue her.
The young demon slayer gets to the harbor on Kirara. Soon, both Kin'u and Gyokuto arrive to help as well. Takonyudo is taken down. Hisui saves the Princess just before she falls onto the rocks. (Uh oh...did her heart go a flutter when he asked if she was ok??)
Princess Aiya rides home with Hisui. Her father discovered what happened giving her a scolding.
That evening, Setsuna trains knowing the urgency for her to get stronger.