If you're looking for manga similar to The Fruit of Grisaia Specials, you might like these titles.
Chihaya is a boy that is looked down because he looks like a girl. Due to that reasons, he isolates himself at home. His mom suggests that he should go to Seiou Academy which is an all girls school. Thus, the story started...
It’s summer vacation and Keiichi’s parents left him with his five younger sisters to go on an overseas trip. Now with their parents far out of the picture, his younger sisters are aggressively making their moves on him. Of course there’s no way he can hold back.
Mizuho can't believe his ears when Grandpa's will is read out. Grandpa's final wish is for Mizuho to attend the same academy as Mizuho's mother. The catch is it's an all-girls school. With the help of his friend Mariya however, he gets a makeover good enough to fool everyone at the academy.
The story revolves around the male protagonist Kohei Hasekura, who transfers into a prestigious public school--an English style six-year school, serving junior high and high school students. The school, named Shuchikan Academy, is on an island, Tamatsu Island, off-shore from mainland Japan, and the only way to get there is by boat. This is a series of characters' introductions to prelude the main story.
The story is once again set in Seio Girl's School, the location of the first game and its spin offs. A beautiful, silver-haired student named Chihaya Kisakinomiya is transferring into the all-female student body at Seio. The catch is that Chihaya is a boy.
Washizuka Shinichiro has just woken up after returning to Japan with his father the hard way, with a collar on his neck and his father gone, leaving a note that he’ll be back in 2-3 years and saying that he’s been left on the grounds of a prestigious school and he’s been enrolled. But before he can get there he has to find the school and use all of his survival skills to get through a high-tech environment gone awry, along with a female student he found sunbathing…