At just nine years old, Kiri leaves his sleepy countryside village to make a living for himself. After a traveling merchant helps him reach a bustling seaside town, Kiri is betrayed and nearly sold into slavery. He escapes but finds himself entirely alone with no money and nowhere to stay.

Wandering the streets, Kiri stumbles upon the Raging Kelpie's Tail, an adventurer's guild. The guild's official rules only allow members who are twelve or older, but the colorful characters working there take the young boy under their wing anyway. The central irony of the story is that despite being officially too young for the guild, Kiri earns his place through determination and need.

The series follows Kiri as he overcomes various challenges under the guild's protection, growing both in height and in spirit. The guild members watch over the earnest boy while he learns to navigate the dangerous life of an adventurer far earlier than regulations would permit. The narrative focuses on Kiri's development from a vulnerable, betrayed child into a capable young adventurer, all while he hides the fact that he is technically too young to be there. His journey involves completing tasks, building relationships with the guild's eccentric members, and gradually earning his place in a world that was not supposed to accept him for several more years.