Yandere male characters in manga usually show an intense, single-minded focus on the object of their affection. They might seem charming at first, but their behavior can become unstable and dangerous as their obsession grows. This can make for a thrilling and dark storyline.
Yandere sister manga often feature intense and obsessive emotions. The sister character might be overly possessive and show extreme behavior towards the protagonist.
To open a manga cafe, you have to have a good collection of manga. Also, create a cozy and inviting atmosphere. Offer comfortable seating and maybe some snacks and drinks. And don't forget to market your cafe well through social media and local promotions.
It depends. If the portrayal of the yandere girlfriend is done in an interesting and nuanced way, it could be appealing. But if it's overly stereotypical or one-dimensional, then no.
Having hentai in manga cafes is a big no-no. It's not the kind of thing that's acceptable in such a setting. Manga cafes are for general reading and entertainment, not for adult-oriented content like hentai.