Recently My Sister Is Unusual Anime

Okay, so, you know how sometimes your family gets… weird? Like, unexpectedly, out-of-nowhere bizarre? Well, buckle up, because my sister's been on a serious anime kick lately, and it’s reached peak “is-everything-okay-in-there” levels.
It all started innocently enough. She was always kinda into stuff like Studio Ghibli (who isn’t, right? Totoro is a classic!), but then BAM! One day, it was like a switch flipped.
Suddenly, her room's a shrine to… well, I’m not entirely sure what. There are posters everywhere. I'm talking wall-to-wall anime girls, some wielding swords, some… looking pensively into the distance? I swear one has actual cat ears. Did I miss something? Are cat ears cool again?
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And the language! Oh, the language. She's started sprinkling Japanese phrases into her everyday conversations. Not, like, common stuff. I’m talking super specific, probably from some obscure magical girl show. Just yesterday, she told me my cooking was "mazui." (Yeah, I looked it up. Apparently, it means "tastes bad." Ouch.)
The Cosplay Conundrum
Then there’s the cosplay. Oh boy, the cosplay. It started with just headbands. Fine, whatever. Cute, even. But now? Now there are full-on costumes appearing. Like, intricate, hand-stitched costumes. I didn’t even know she could sew! Is this a new hobby? A cry for help? A carefully planned takeover of the house?

She’s even started referring to me by honorifics! The other day, it was "[My Name]-san." I just stared. I’m her brother! Since when are we formal? Am I supposed to bow now? Should I start calling her "Onee-chan"? (Please, someone tell me I don’t have to do that.)
The music is another level of commitment. Forget her usual pop playlists, now it's all hyper-kinetic J-pop and dramatic orchestral scores. My ears are constantly assaulted by tunes I can't even begin to understand. I feel like I’m living in the opening credits of some high-stakes, anime-style drama. Is this my life now?
Anime Obsessed: Good or Bad?
Look, I'm not judging. Okay, maybe I'm judging a little. But I get it. Everyone needs a hobby. And if anime makes her happy, then who am I to complain? Besides, some of the shows actually look kinda interesting. (Don’t tell her I said that.) The animation can be really stunning. And the storylines… well, they’re certainly… something.

But still, I worry. Is she getting enough sleep? Is she eating properly? Has she seen the sun lately? Am I the only one noticing this dramatic shift in personality? Am I going crazy?
So, I guess what I’m asking is, is this normal? Is this just a phase? Should I stage an intervention? Maybe slip some vitamin D into her ramen? Or should I just embrace the chaos and learn to appreciate the artistic merits of a grown woman dressed as a magical warrior?

Maybe I should ask her. Nah. I'm afraid of the answer. And I'm definitely afraid of what new phrase she'll use to describe my culinary skills if I bring it up. "Kuso umai"? (I looked that one up too... it means "extremely delicious". Don't think I'll ever hear that one.)
Anyway, anyone else’s sibling suddenly become an anime aficionado? Share your stories! Misery loves company... and maybe you can give me some tips on surviving this unexpected transformation. Help!
One thing is certain, my sister's anime obsession is making life never dull! But seriously, what anime should I secretly watch to understand what's going on with her?
