It's the legitimate 16th century Tsurumaru Castle. The bus seems to have gone completely unnoticed to anyone around, despite it being rather obviously far too futuristic for this place.
((Well, that's my cue to try writing with a bit more length.))
It was not as he remembered it. Of course it wasn't. It has been twenty years, possibly more. Twenty years for humanity's ashes to scour away his memories. Twenty years of fighting amidst the ruined spires and twisted concrete. Twenty years to repaint a hazy canvas with romanticized brushstrokes. And yet, as he gazes across the country side, the azure sky and green fields belying the promise of bloodshed, the earthly scents rising from a broken country, it beckoned to him. The home he had, the life he had, the world he had lost. Beckoning him, like a siren's call.
The bus stops. The doors swing open. The castle is nowhere to be seen. And it won't be seen for another few years, what he could see now however, are banners, the Shimazu
mon proudly emblazoned on them, perfectly matching his helmet's emblem. The men beneath them perfect strangers, yet oh so familiar in stance and dialect. He was finally home. After all those years. Home at last.
"<Surely, surely I'd be heartless, had I never wished for this.>"<And surely I would be a fool to step out now.>What did he have to return to? He could no longer recall his commander's name. He could not remember the rush of a cavalry charge. He couldn't even remember his mother's smile, nor his father's embrace. What was left? A pneumatic hiss. The doors slam shut. The bus turns around, the sights now playing in reverse. He presses a gloved hand against the window, tears falling in silence, hidden within his metamaterial tomb. As the final visages fade from sight, his arm falls, parting with the glass. With a sigh, he stretches and reclines in his chair, softly intoning a melody at a tired pace
"It was, a big, big world, but we thought we were bigg-er, pushing each other to the limits, we were learnin' quicker, by elev-en smoking herb and drinking burn-ing liquor, nev-er rich so we were out to make that steady figure... Once, I was ele-ven years old, my dad-dy told me, go get yourself a wife or you'll be lonely... Once I was eleven years old..."Closing his eyes, he pulls out a metal locket and flicks it open. In his mind he sees an adolescent girl, her lips thin, her face slightly chubby, with a kind smile like her father. The dark hazel of her eyes shining with youthful energy, yet tired from one too many nights staying up reading. His eyes snap open, the picture in the locket perfectly matching the girl in his mind.
"Heh, she really does take after you, Sam..."