This fanlisting is for Kanojo-tachi no X-Day, an extremely touching, poignant manga (at least in my opinion ^_^). After reading the first book, I feel in love with it. After reading the second, I cried for days. Even before I read the manga, which my friend suggested to me, she dubbed me "Polaris" for one of the main characters. That still stands as my nickname XD
The manga itself is a two-volume series following the life events of Saginuma Rika, Shimada Nanaka, Tsukumura Yumihiko, and teacher Katano Reichi. They all have problems of their own, but after meeting online in a chatroom and Rika jokingly suggests blowing up the school, it turns into a long-lasting friendship between the four.
The name comes from the chatroom in which the characters first meet. Ursa Minor, a private chatroom conducted by Polaris. The clues are "tail" and "sleepless nights". After a while, Rika pieces everything together and becomes one of the "chosen" to perform X-Day.
Anyway, I'll stop myself before I start turning this into a huge lecture about why I love it so much and the characters and such. Just join already, lest I brandish my cell phone at you!