A strange new transfer student joins Akira Tsubaki's class - her name is Mikoto Urabe and she has the habit of hiding her face behind her hair and falling asleep during class. One afternoon, when Akira goes to fetch his bag from the classroom, he finds Mikoto sleeping alone at her desk. She wakes up and makes her exit, but leaves behind some of her own drool on the desk. Without thinking, Akira tastes the drool... and is surprised to find it has a sweet, delicious flavour! A few days later, and Akira mysteriously comes down with a high fever; he's confused as to what is wrong with him until Mikoto visits him and tells him he's addicted to her drool and is suffering from withdrawal symptoms. From now on, Akira will need a regular top-up of Mikoto's saliva or else he'll fall ill - but maybe this isn't such a terrible thing, considering that Akira is falling for Mikoto...
Sawako Kuronuma is just like any other high school girl who wants to make friends and be useful. The only problem is she bears a worrying resemblance to Sadako from 'The Ring!' Because of her reputation, people are not only terrified of her, but small dogs even bark in fear at her presence; in fact, the only person in school who will talk to her is the lively class hottie, Kazehara. As the pair spends more time together, Kazehara slowly begins to bring Sawako out of her shell and soon their feelings for each other develop further. Though with her crippling insecurities, lack of social skills, and a series of cruel rumors and misunderstandings, it seems that Sawako's dream of a normal life won’t be quite so easy to obtain.
Both series feature a strange, spooky, and unpopular girl who sits alone, until one boy seems something special in her and initiates contact. In both series the pair find themselves in a close relationship, in which they have doubts & uncertainties about their feelings, their partner's feelings, and the overall status of the relationship.
Both mangas are cute and unusual Seinen romances. Both are a stories about really weird high school student (boy in Love Roma, girl in Mysterious girlfriend X ) suddenly starting a slightly bizarre but really charming romance with a normal student. Whether it's complete honesty and ability to express your feelings in front of a large crowd (Love Roma) or a relationship based on drool, that can convey emotions (Mysterious Girlfriend X) those unusual stories are very heartwarming.
Both mangas are trying to answer some relationship questions (like how to understand the other person, or what dating each other means). The main difference is that Mysterious Girlfriend X is a bit more on the ecchi side, and Love Roma is more on the absurd side.