It’s like backwards-engineering a narrative database -- and you may be surprised to find how much the story changes when you focus on a different partner each time. Hakuoki is a period piece, taking place in the Bakumatsu period of Japan at the time of civil unrest between the Emperor and the Shogun.
Dating simulation games started gaining popularity in Japan during the 90's.
Welcome to Otome, visual dating games made with women in mind.
Steam on the other hand, has made digital distribution cost-effective, efficient, and accessible to a massive audience.
All this is a huge boon for visual novels and dating simulation games, which would have lingered in obscurity outside of Japan, otherwise.
However, this was never the case in other parts of the world.
Video game magazines that I read regularly would cover Japanese imports and niche titles, but dating sims were merely a curiosity and nothing more. The games industry has grown exponentially and modern gamers are interested in titles beyond the scope of the action, shooting and role-playing genres.