I fist saw No More Dream and really really liked it, looked them up and realized they were a rookie group so while I liked them and the song I didn't Stan them (because, for me, stanning a rookie group is so risky because you don't know what they're going to do in the long run and so I don't put much energy into them) and my bias group at the time was Infinite so I was well distracted. But I still listened to No More Dream and the "2 cool for skool" mini, just didn't go into the fandom which I assumed was non-existent at that point. I admit I missed NO and "O!RUL8, 2?" Era because I was too busy with infinite. but they got me back quick with "Boy in Luv" again, randomly stumbled upon it. Now, backdrop to this, during the time I was distracted with infinite, I had been seeing some really cool dance gifs making their way around Tumblr at that time and had them saved because I didn't know who they were (weren't tagged and was too lazy to investigate) for a long time. They were gifs of the Concept Trailer and We are Bulletproof part 2 and Boy in Luv (all dance practice versions) I thought (no joke) that it was a kickass dance team. Made no connection whatsoever. So when I saw the Boy in Luv video I had two thoughts
A. This song is good holy shit, I love this.
B. This dance looks really familiar.
So I went back to Tumblr after watching the Mv and sure enough the dance was the same so I went back to YouTube and looked up the boy in luv dance practice and saw them linked to the other dance practices. My mind was blown that this group I listened to was the same group that I was seeing on tumblr and the same group that I loved the debut MV/ mini album for and I just never made the connection that these three groups were actually all 1 group, because like I said, I didn't even think that they were a kpop group, I thought they were a dance team. So I immediately watched their live stages to see how they were live and they were great! Then I went to watch rookie king to see their personalities (I can't stan a group until I like all aspects of them, it's a long process and why I only have 2 loves. Must love all members attitudes and personalities, a majority of the music, must be good live performers, must have a hand in writing/producing their own music, etc. in other words, they must be exceptional to other groups. I sound really elitist but, to me, that's what sets certain groups apart from other kpop groups. Also the personality thing is a hurdle because I can't stan a group if I love all the members except like 1 or 2 because that's just not fair, in my eyes, and exhausting. I tried to do it once, it didn't work out.)
So yeah, discovered them during No More Dream, unknowingly thought they were awesome between No More Dream and Boy in Luv. Fell hard and never got back up.
My first groups I loved. Like you, were Backstreet Boys and N'Sync lol I'm in my late 20's. First kpop groups I loved were Big Bang and 2NE1. Now Infinite and BTS, though I still like Big Bang and ...2NE1