Yoji

A kind boy who always helps those in need,
Yoji is good-natured and has a strong sense of duty.

Kei

A passionate machining enthusiast with
dexterous hands,
Kei is an outgoing yet somewhat naive girl

Kelly

The only daughter of the richest family in town, and Kei’s classmate.
Harbors a secret and strong sense of rivalry when it comes to Yoji and Kei’s adventures.※Appears in Episode 2

George

Butler for Kelly’s family.
Takes care of Kelly,
whose parents aren’t often around
because of work.
Worries about Kelly all day long.*A character since FASTENING DAYS 2

Anna

Anna, a widow, is a gentle woman
living in her family's house up on a hill.
She took in and raised Yoji and Kei,
who are orphans.

Oscar

Anna's husband left behind this robot bear
who understands human emotions.
He always looks out for Yoji, Kei and Anna.

Samhen

A young boy who lives apart from his parents for the sake of his studies and transfers into Kei and Kelly’s class. A little shy but very kindhearted.※Appears in Episode 4

Jack

An autonomous robot equipped with highly advanced emotional AI (emotional information processing). Sometimes a little too chatty, but always Samhen’s most trusted ally and friend.※Appears in Episode 4