"Either way, she haunts him"

but I won’t stop until that girl is mine.

I finally arrive at Bakumatsu era and ROTR characters’ silhouette makes me💔

But...something something. The Blade twin's upbringing in the Kurosu Clan being one of complete dehumanisation. They cast their names aside in the name of "burying the past". They're taught to function as weapons not people.

"The two of us are one," There is no 'individual' when you're a blade twin. You exist only as your twin exists. There is no "You" only "We".

But human beings need to find identity. The Blade Twin who can't get over what happened in their past. A defining moment they were never able to move on from. Their development as a person was literally stunted right after they lost their village. They're ripped from their twin and what happens? They need a purpose...and it's one of taking the world down with them.

Vs the Ronin, who also can't fathom who they are without their Blade Twin. They go out to find them, and in the meantime, they're actually forced to develop an identity outside of their Blade Twin thanks to Ryoma and the other bonds they make.

If the Blade Twin had asked the Ronin to join them right as the game fully starts. They would've agreed. It's because they've forged themselves beyond them that they realise the Blade Twin will only drag them down a road they want no part of anymore. Looking to the future of Japan instead of the past.

It's also why the Blade Twin targets Ryoma. I think there's a genuine fear that their Twin is able to move on and forge their own identity while they're stuck in the past. The fear of being "replaced" and left with nothing when ALL you've known is being part of a duo.