It's ok for a little kids' book and can be twisted for a Studio Ghibli-like movie!!!
And then we may learn the sword's deal was the girl's father was a wizard and the girl was one of those "always sick and always about to die" generic female character so his father finds an another dimension where there is no "death" (something like heaven but more like another dimension seperated from physical reality) but to cast the spell to send her daughter to that place she had to die. To fix this dilemma he decided to "kill her" and send his soul to this separate dimension but to make her "exist as a living person" he had to take his own life force and give it to her daughter's death body during the ritual he performed.
The ritual was in a way that the moment she died and sent to this another dimension her father give her his own life force to make her "live again", but as a result his father would die, but he used a very tiny bit o his life force into his sword and sent this sword with her to protect her in the unknown dimension.
The result was his father turned into a sword having no mind of his own to even think but only animated by the sense of protecting his own daughter and the girl lost her memory.
The ritual could establish a connection to this dimension by locked on to the place there that has the most intense sign of "magical energy of its own kind" which was this ruin. Then we will learn this ruin was a place to travel between dimensions but since last of wizards are no more there due to an evil monster who feeds upon magic people there forgot what was magic and what's up with that ruin. To them magic was a BS people back then came up with for stories. But since this evil monster ate anything that has magic power to prevent itself from dying he was sleeping for a long long time enough to turn into a giant statue that made people think it was just an ancient statue made by ancient people in the middle of nowhere but after the girl and the sword arrives with magic and the sword basically "alive" because of magic this monster wakes ups and transform to its real self from this statue form and hunt down the girl and her sword.
Then the monster being awake people are like "WTF" and have to face with the concept of something endangering their life when they have no concept of dying at all. Monster can kill them but he rather has no point to attack them, but just because they get into his way with a BS sense of forming an army but they are more after scolding this monster barely because they also never thought about the concept of weapons and even talking bad and whatnot they are naturally killed by the monster on the way.
The sword attacks the monster several times to protect the girl and in the end sword was eaten by the monster. The moment we start to think "damn son the girl is fucked now" we see a bright light coming from the monster!!!! It turned out the sword was getting power up from the monster because by eating tons of magic power it became a magic station that fueled the sword!!! So the sword sucking all the magic energy to itself monster simply stops existing like a defeated Pokemon!!!! And then the sword having so much magical power it explodes but more like unleashing too much energy to the realm of this reality making everyone have magic powers and then the sword turns into girl's father.
Then the girl also remembers who she was, what her father had to do and what the sword was. They hug and all but her father says "My dear daughter, I don't have much time. I hope you'll live a happy life!!!" and the girl screams and crys "No papa, don't go!!! Don't leave me like my mama did!!!!" and the father smiles sadly and says "look at the sun!". The father starts to disappear party by part by turning into light and he says "I will never fade away, I'll always watch you from the sun"! And then girl says "papa you may watch me but I can't look at the sun, that shit is too bright!!!" and the father says "LOL" and dissappears for good. FIN!!
I also thought of the 2nd movie!!!
It turns out the ruin was developed as a gateaway to create the physical world the girl and her father came from. In our understanding it was a "online video game" but more like magical version of it!!! People from another dimension was using the people in the physical world as avatar to play "the game". However in the physical world an evil mage figured about this and reversed the roles!!!!! He found a way to use random person in this another dimension as his own avatar to fucked the world!!!! It's like video game character hijacked real life person in our world!!! What will be the girl who is now a grown ass woman will do!!!! lolol
