Here she's a SMART sex object:Trapped in unknown world with a huge risk of becoming a sex slave by corrupt government > choose semen suction instead of survivability skills.....
Is there any fantasy manga which not portray FMC as a dumb sex object?
And romanticizing Japanese history in a fantasy story (the Shinsengumi was also the shogun’s secret police which is also sketchy, but that’s neither here nor there)