I was into Japanese before Korean. I'm not exactly sure how I got into K-pop (it was sort of part of my life before I knew it lol) but I think it was Younha. She sings "Houki Boshi" from Bleach if memory serves me right and I was amazed that she was actually Korean. My sister made me listen to "Password 486" and I totally loved it.
I sort of knew Super Junior/SNSD/DBSK existed, but I never searched them up and stuff. I knew their songs, though (Sorry, Sorry, Gee/Oh, Mirotic lol) I remember SHINee & Big Bang songs, so I think I can say they were my official first? Up until I graduated high school. (Girl groups include 2ne1 and random songs like Chu by f(x) and Abracadabra by BEG.)
College was the start of the over-the-top drama watching and K-pop listening. (Before college, I went to bed like regular people haha) The groups I became obsessed with after SHINee/Big Bang/SuJu died down were EXO (I can't even begin to describe how crazy I was lol) & B2st. Watching all their MVs and shows etc (Other groups like 2PM, B.A.P, CNBlue, F.T.Island, B1A4 just found their way into my life.)
Currently I'm head over heels for BTS. I got a whiff of them back when they released Boys In Luv, and although it was a nice song, it was a bit different to what I was used to so it didn't really hit me until after I Need You and Dope came along and they just stole my heart in a matter of minutes. Now I can take a national exam on BTS and probably score a 90% on a bad day. xD