The core theme of the Lost Children Chapter in Berserk is ''Escapism''. Children dream, imagine, yet are limited by the cruel world that adults have created for them. (a thread)

To put this theme into the forefront we follow the journey of Jill&Roshine.

Roshine was inspired by the fairy tail of Peekaf and struggled under the household of her parents, where her father thought that he isn't her true dad due to her mom being raped in the war.

Suffering under these circumstances, you had Roshine constantly running away from her household, ultimately reaching mist valley and escaping that life by sacrificing her parents.

Meanwhile Jill also finds her reason to leave her village, similarly suffering under her father.

This is where Guts comes in. Someone who is known to struggle and struggle. His world is enveloped by Darkness, and thus not a paradise Jill can escape to, but instead of seeking escapism, she ends up building from her experience with Guts and confronts HER world. U gotta love it

In general children in Berserk represent more than just a demographic. They serve a thematic purpose for the fantasy world of the series.

Children are more accustomed to magic and astral creatures like elfs, because of their vivid imagination and belief. Meanwhile Adults

are accustomed to a life of religion&faith, living in a feudalistic society that limits their worldview under the the influence of one doctrine, most likely a result of the GH.

There is a reason you have many children in Elfhelm and why they are best suited for learning magic