The Sister Paradox

Liam is his parents' only child, and that's just fine with him.
Until the day the sister-he-never-had shows up at school.
Just to make it worse, the sword-wielding Kari tells him they have an important quest to complete.
And that's how Liam finds himself dragged into another world, facing basilisks and unicorns, cursed objects, elves, and even a dragon, all magical and dangerous, but none more so than the sister he didn't have until that morning. A sister who turns out to be quite good with her sword, and ready to use it when faced with things like a dragon as long as her brother is at her side.
Liam begins to realize two things: it's going to be a very long day, and having a sister can be weird.
But most unsettling of all, he's not sure he minds…