Mysterious Girlfriend X (謎の彼女X / Nazo no Kanojo X) was a monthly Japanese manga written and illustrated by Riichi Ueshiba. Originally published as a one-shot story in 2004, it soon became a serialized comic in Kodansha's Afternoon magazine in 2006. The manga finished in September 2014, ten years after it began.
An anime adaptation by Hoods Entertainment began airing in Japan starting on April 7, 2012 and ran until June 30, 2012, with an Original Video Animation episode released on August 23, 2012.
The opening theme music is " Koi no Ookesutora ( Orchestra of Love ) "
- Lyrics by Yamada Toshiaki
- Composed and Arranged by Kitagawa Katsutoshi
- Performed by Yoshitani Ayako
The series follows the romantic but unusual relationship of Akira Tsubaki and Mikoto Urabe. Urabe is a mysterious female transfer student who recently came to Tsubaki's high school. After a series of strange events, Tsubaki finds himself addicted to Urabe's drool. She claims the addiction to be "love sickness", and their relationship slowly progresses, focusing on the odd friendship and behavior that comes out of their drool attachment.
The plot covers the various relationship developments for the couple, and how they're able to deal with or overcome them via their special bond. Somehow, the drool allows them to experience what each other are thinking or feeling, and allows for a better understanding of each other, more so than any other couple. However, because Tsubaki has never had a girlfriend, and Urabe has never had a boyfriend, and because they both declare to each other that they are virgins, they do like to take things very slowly, with intimate aspects of their relationship being experienced very carefully, many times by trial and error. This aspect, among many other quirky happenings, leaves the reader or viewer wondering when, or if, they will ever kiss.
Nevertheless, as the story progresses, the relationship between the two deepens into genuine, pure love. The manga strongly foreshadows their souls becoming deeply intertwined, and that they will never break up, but rather will stay together and be committed to one another for life.
In both the anime and the manga, the exact time period of the series is hard to place. DVDs seem to be commonplace, but a lot of the scenery and technology is very reminiscent of the 90's, and no one has a cell phone. This forces Urabe and Tsubaki to talk more face to face, rather than via text message or email, which is important because communication is a main theme throughout the series. Cell phones do exist though, as adverts for a 'P-Phone' with Momoka appear in the background of some manga panels.
The manga includes a very wonky timeline though: Tsubaki and Urabe meet in their second year of high school while everyone is still wearing their summer outfits (presumably in late September or early October, but before late May or early June, going by chapter 14) and before the summer break. The pair go through many uniform changes over the course of the manga, and reference multiple summers and winters that all seem to proceed each other.
One theory is that the manga jumps around the time the two spend at school as the author sees fit, focusing on specific adventures here and there. There's evidence for this in the way Tsubaki and Urabe celebrate their first Valentine's Day together as late as chapter 75 (along with their first Christmas, New Years and White Day together in the surrounding chapters), even though a storyline in as early as chapter 14 covers Urabe changing into her summer uniform the June after they met.
By all accounts the pair should be in their third and final year of high school by now, and probably near the end of it as well. They'd also very likely be 18 years old now, although no chapters have covered any birthdays, exams or moving up a year and/or changing class.
The simplest and most probable explanation is that as the manga continued on through the years, Riichi had more and more seasonal ideas for their relationship to encounter and just wrote them as he saw fit.
(NOTICE---Please enjoy this Mysterious Girlfriend X Wikia, but realize that it contains SPOILERS throughout, so read and act accordingly ! )