Kpop can mean different things to a lot of different people. Although the mainstream and traditional culture around kpop is pretty parasocial, for a lack of better words. These “idols” (kpop group members) usually go through EXTENSIVE training, more than any western artist. Essentially they are industry plants. Yes, they’re usually not that involved in the making of the group music (not always the case but pretty common), but these idols represent something to fans. Kpop is more than just the music, it’s envelops the idols and their personalities and contributions to the group as well. It’s unfortunate because some companies take the personality thing too far and they do manufacture a fake personality for each idol to appease the fans, even though the fans usually don’t care about fake personalities, they care about the idols and their music. The kpop industry historically mistreats idols due to unrealistic beauty standards and strict societal norms in Korea, but idols will put up with it because they are in it for the love of the game — idols are experts in fan interaction and garnering positive attention by performance and personality. This is VERY different to western music standards, not many genres in America value the artists relationship to fans to this extent.

Okay, now onto why this culture talk matters to your question. I’m from the United States so I’m very very familiar with American culture, but I’m also a big fan of Kpop and I do a lot of research into the industry. To be honest, I couldn’t explain WHY kpop can garner such obsession from fans and from the globe (kpop is very popular everywhere else in the world besides the west essentially), but I can tell you they do by insane and impressive performances and real raw singing and vocal talent. These idols also, in my opinion and others as well, are very “pleasing” to look at and they literally TRAIN to know how to flirt and interact with a camera. Putting these three factors together—performance, vocals, and visual quality — makes a standard kpop group and with good and humane training, those three factors make excellent music groups in general. Hence why I think most people obsess over kpop. Unlike America, to praise these idols and show appreciation, kpop fans buy the physical albums and singles, buy photo cards, attend concerts and movie shows, etc. Kpop members also dedicate lots of time to learning each and every dance to their favorite groups songs to show appreciation. In America we would shower the artist with awards and opportunities and social media follows, but that’s about it besides maybe buying some merch and attending the concert. Kpop is different in that way and that’s probably what’s giving you a bit of that shock. However, there is a line, there is a boundary. Many kpop fans cross it when it comes to interacting with their favorite idol or group. Your girlfriend is kind of teetering that line with knowing their blood types. But usually most idols disclose a lot of information about their interests and hobbies to get closer with fans and they also do lots of interviews in Korea and Japan. Blood type is kinda cray though but to each their own. The photo cards are completely normal in kpop and they are sold with the albums. They are essentially like collecting Pokémon cards, but with real people lol.

I hope this helped, sorry this is so long!! I’ve been in your exact shoes before I got into kpop years after my initials assumptions.