Nazo no Kanojo X (Mysterious Girlfriend X) was an accidental manga for me. It happened to cross the page on my iPad when I accidently touched it's link. I was very annoyed at that time, because I just saw the part when Goku dies in DragonBall Z. However, I just decided to read it anyway.
The first chapter was very weird, because I was felt like critiquing the art. I was like... What is this? But after reading a couple more chapters, I was completely hooked onto Urabe Mikoto and Tsubaki Akira. I loved the drool bondage between the two of them, because it was a refreshing type of relationship for me. Soon after, I spent most of my day downloading and reading all the chapters. Even while I was sleeping, I was still thinking about how awesome it was. I love all the times when other girls come between Tsubaki and Urabe, abd I also loved especially chapters 37-48, when Urabe and Momoka get mixed up. That was I really started getting addicted to this manga.
This series was truly the best I've read. Even though the art-work isn't the best at the beginning, it gets better, and the plot and characters really made it work for me. I'm still addicted to re-reading this manga, even though I only started reading it 2 days ago. IT IS SIMPLY AWESOME and I really hope Riichi Ueshiba keeps up the good work, and continues to produce such high quality manga.