Fifteen years ago, natality decreased greatly in Japan and the few who were born during that time are called the "LastGen."
Hanasaka Haru, a 15-year-old LastGen kid, has never met any classmates before. Now, he goes to school for the first time and meets Himeshiro Sakurako. But Sakurako is not quite the ideal classmate he imagined, and his dream school life isn't turning out the way he wanted it to...

Tetsuro Tanaka is a month late starting high school due to an accident. As he's finally able to go, he's almost hit by a truck, but is saved by a mysterious girl who wears the same pendant as the one that his school has. He finds out that he's the only boy in his class and is instantly hated by his classmates except for a few. One girl is Yayoi Asuka, whose name Tetsuro is familiar with as it's the same name as a girl he knew when he was little. A few more girls get introduced, one being Sakuya Kazamatsuri. Yayoi reveals that she has superpowers and she takes him to his dorm, which she is going to share with him along with Sakuya, Miyabi Tsukuyomi, Akio Suzuka, Otome Chouno, Hifumi Inokai, and finally his teacher, Kano.
(Source: Lunar Scribbles)

A classmate learns that Minazu Aruto loves reading novels and short stories so she recommends a club that the school has called the Philosophia. The classmate doesn’t really know what the club is about but the name sparks a curiosity in Aruto and he decides to find out what it is. He goes to the old library on campus where he meets and is introduced to all three members of the group: Tomoe, Takaho and Kaede. Without really being explained what the Philosophia club is about, Aruto finds himself joining what he thinks is a literature club.
(Source: MangaHelpers)

After his mother died, a 15-year-old boy named Taro is invited by his grandfather to the Hanaukyo mansion. Soon after he arrives, his grandfather disappears, and Taro learns that not only will he inherit the unbelievably huge estate, he will also have access to the countless beautiful young maids working there.
(Source: MU)

Miyano Amata, known as the "Perfect Prince" for his intelligence, looks, and cool personality, is asked to substitute for his sister as an attendant at a doujinshi convention disguised as a loligothic girl. There he meets a girl from his class and they become friends, but he must crossdress in order to be with the girl while learning about the fujoshi fandom.
(Source: MU)