First things first, I am never going to claim to know anything and everything. This is and always has been my thoughts, reviews, and opinions; in this case opinions being the key term but if I am able to get proper facts in then I definitely will. What is a fact for sure is that Western and Eastern culture is drastically different and that does have a lot to do with this. In Western culture these types of either obsessions or relationships are both illegal and incredibly wrong, thus why they are rarely talked about or brought up. However from what I did look up is that in Eastern culture, particularly the past, it was a very common practice for cousins and family to be in such practices. However, even there it is greatly looked down upon as well, and with good reason.
With anime being Japanese, an Eastern culture, it isn't as taboo to include as a topic or touch on as a subject in their shows. It can make Western viewers uncomfortable occasionally but most anime fans just roll it off at this point because it happens often, it's just another trope in the very long list of anime tropes.
The one most common example of this kind of relationship in a very popular anime that got a lot of people very uncomfortable was in Sword Art Online. Now, with Sword Art, it's a very popular show and has become one of those "starters" for some people nowadays. That's where one particular angle that occurs in the 2nd season and kind of lingers even after it's "resolved" is the relationship that Suguha wants to have with her brother (they make sure SEVERAL times to say he's her cousin actually) Kirito. It became a big turn off for the show for several people I knew, like they could handle the show and stuff but that topic nah just too far into left field. While the show has had ups and downs a lot of people find this particular thing something that they honestly didn't need to do.
Now why bring this up as a topic in general because it seems to be an uncomfortable one ??
Well, with recent shows like "Eromanga Sensei", the siscom character in "Black Clover", and this seasons "My Sister, My Writer", and tons more as well it seems like these types of tropes are getting touched on more and more than ever. Why is that though is what I thought ?? Is it because with a character like Sagiri from Eromanga Sensei that fans all just saw her as a cute character and sympathized with her ?? That could be one reason. Could these shows, being as mainstream in the new seasons of anime as they are, be making this trope more normal (or about as normal as you can make it) ??
To be honest, I'm not 100% sure myself.
I find the trope can be used in one of two ways and that's what determines how I feel about something this wrong being used in a show. If it's a serious situation or a creepy situation (like the obsessions) then no I'm totally against using this trope for that. However, a lot of reallly good shows have used this trope for comedic purposes and that's when I'm ok with it being used. One of my favourite shows is Grand Blue, in it the main female protagonist Chisa is embarassed by her passed out drunk cousin Iori at a pageant but she decides to "thank her boyfriend" and points at him in order to use Iori as a way to detract hundreds of guys hitting on her as she is one of only 3 women in the engineering program. So they aren't really dating but they use the whole thing in order to kind of save Chisa and it leads to a lot of funny moments, particularly the group of guys Iori becomes friends with because they are so jealous of him. Just amazing that show; it's also a great example of using what is generally a gross trope and turning it into comedy gold.
It's always going to be something in anime you're going to need to learn to deal with as a fan and I think that's why it's something to be brought forward. If you read my articles and plan on watching any anime at all, like start to get into it for the first time, just prep yourself for a different world. One that is relatively uncomfortable with several topics like this.
Totally uncomfortable. Ya, it really hurt the 2nd season of Sword Art Online......just to reiterate my point (I think that's what has a lot of people discussing this). It is an uncomfortable thing.