Himeko

She was sitting on the star express and waiting for the others to return from the mission.

But now, it's packed with a molecular saw, an escaped satellite, and countless other contraptions — the embodiment of her whims and the proof of her resolute will.
No travel companion is more faithful to her than this suitcase. Passengers come and go on the Express, and perhaps not even "the conductor" would be able to accompany her and the Express from start to finish.
But she doesn't care. She didn't care when that pretentious blond man left without saying goodbye, just like how she didn't care about her distant homeworld and old friends.
She knows that this journey is lonely. Even if she could get to know like-minded travel companions, even if they showed her generous grace, even if she could witness the end of a complete journey with those companions — that's all just a momentary fluke.
She knows that this journey is lonely. Nobody can follow in the exact same footsteps as anyone else. Nobody can experience for someone else everything that happens along a journey. All she can rely on are her own two eyes and feet.
That's why she stores inside her suitcase all the sights her eyes have witnessed, and all the footprints her feet have left behind.
Himeko's memory is very good.
The longer the journey gets, the more travel companions she accrues. She can still remember many of them.
She remembers her awkward chit-chats with Pom-Pom, and how the first two passengers aboard the Express were Welt and his blond friend. She remembers how the taciturn Dan Heng defeated the monsters that can swallow stars with just one strike of his lance. She remembers how March 7th had awoken from her icy slumber, all the outfits she'd designed for March, and what March loves the most. She remembers how the Crew arrived at Herta Space Station, how she met (Trailblazer), and how they'd embarked on a new journey once more.
She remembers the specifications for every single component of the Express and how they're assembled.