WARNING: The following contains spoilers for Dragon Goes House-Hunting Episode 12, "A Well-Defended Home," now streaming on Crunchyroll.
One of the major themes in Dragon Goes House-Hunting is parenthood -- more specifically, fatherhood. The series started with Letty being kicked out of his home by his father, which began the whole house-hunting journey. Then he found a foster father of sorts in Dearia, who taught him everything about the world.
Soon, Letty himself became a father to Pip, and then Nell's fight with her father is what led her to Letty and Dearia. So it's incredibly coincidental (or not) that the series finale just happened to air on Father's Day, and it comes back full circle with Letty gaining a fuller understanding of fatherhood.
Episode 11 of Dragon Goes House-Hunting ended on a small cliffhanger with Nell and Letty being stuck in the royal palace -- the home Nell had escaped from. She is still not ready to forgive her father for eating her cupcake, so she decides to go to war with her own kingdom.
Nell's father, the king, rightly assumes she is being kidnapped by the Flame Dragon Lord, aka Letty, since he did show up together with her. So the king leads the army to attack his castle in hopes of rescuing Nell from the vicious dragon. Nell and company are completely outnumbered -- including Pip, there are only four available combatants. Luckily, Dearia is armed with extensive knowledge of the castle's defense system and some gnomes for hire.
Dearia shows Letty and Nell how to properly defend the castle with its existing infrastructure, including a moat and drawbridge, multiple gates, three defensive walls, trap doors, and many winding pathways all designed to prevent a lot of people from entering at once. With the added help, Letty and Nell are able to defend the castle for a whole day before the gnomes finish their shifts.
When the gnomes leave, Nell and Letty retreat into the palace and let the army enter. Letty decides to help Nell and her father by using himself as a decoy to lure the king to Nell's hiding place. Letty knows Nell is ready to forgive her father after he calls his daughter the most precious thing in the world to him.
The king first checks to make sure Nell is unharmed and immediately apologizes, agreeing to let her eat any cake she wants. With a father like this, it's no wonder Nell is so spoiled. But he is also a fair and understanding king who wants humans and non-humans to get along. After Letty and Dearia explain the situation, he knows that Nell caused all the ruckus and wants her to repent for this, showing he can actually be a responsible parent too.
Seeing Nell and the king makes Letty remember his own father, who he realizes may have kicked him out to force him to grow and be independent. Letty has learned a lot throughout this journey, and he can now see things from other people's perspectives instead of pouting and blaming others, a major sign of maturity. He has also learned to put the well-being of others ahead of his own in order to protect those he cares about, another trait of a good father.
Since the soldiers are still searching for the Flame Dragon Lord around the palace, the king and Nell help Letty escape from the window. The king gives Letty his treasured fairy dust so he can fly out of the castle. Nell gives her dragon friend a kiss before saying goodbye and vows to go find them again once things calm down.
Seeing Letty fly for the first time, finally able to see the world the way he's supposed to, is quite fantastical and majestic. Through his journey with Dearia will likely continue for a long time, he has already become a much better dragon than when he started, thus this is a wonderful way to end Dragon Goes House-Hunting.
