Around the the 37th year of the Meiji Era (1904) in the midst of the Russo-Japanese war, the small Japanese army, in need of assistance, uses its special flying (thanks to a benevolent demon) ship, the Amanohara, to attack Russia's major base at Port Arthur (Lushun).Umakai Shintaro, a Russian diplomat originally from Japan, defects and goes to Sapporo to teach at a girls academy. However, that girls academy is not typical - it is on board the Amanohara, and the five girls Shintaro teaches are known as the Lime Unit - girls with the ability to summon powerful beings to fight for them.Based on the visual novel of the same name.

A sequel/spinoff of the Alice in the Country of Hearts manga. It’s happy ever after for Julius and Alice who are now lovers. But married life with the morose, antisocial workaholic Clockmaker is not without its problems. Now a “crazy storm” that is said to change everyone it touches is about to arrive. What further adventures are in store for Alice Liddell in this strange Wonderland?

From ShoujoMagic:

After failing the entrance exams to her school of choice, Hiyo Osora gets an acceptance letter from SM Academy. But she didn't even apply or take its exam! When she arrives, there's something amiss -- all the students are... monsters!? And the head of the student council says he's her fiancé right before he sprouts giant black wings! What strange fate brought Osora to SM Academy, and what supernatural fate awaits her after this!?
*Volume 9 contains an extra story called Kitakubu.

Love Rush is about monsters who fall in love with the main character, and they all want to marry him.

Kensuke is your usual high schooler. He's unattractive, unreliable and leads a very boring life. This all changes in one night, when a goddess granted him his wish and makes him a popular boy. And soon after that girls start flocking to him like there is no tomorrow. The first dramatic change in his life came from his sister and the second was a childhood friend that he had no idea existed. Things don't just stop there, soon all sort of weird girls come knocking at his door. These girls ranged from Nekomimi, Magical Shoujo etc. His love drama filled life is about to begin...

Ryou's mom died when he was young, and his dad is always at work. Now with a new girlfriend, how will his life be turned upside-down when he finds out a classmate of his is going to be his new stepmother?

From Tokyopop:
Yuuichi Tate is overjoyed: He gets to go to a brand new high school. Of course, then he just happens to find out the school he choose is under frequent attack by strange creatures called ''Orphans'', and the school set up a special task force of female members called ''HiME''s, using various elements as their powers, to battle these invaders. That's not all, though. Each member of the HiME task force has their own, unique ''Key'', another person whom, upon being discovered, can team up with the HiME to create a ''Child'', a combative unit specifically needed to effectively battle these Orphans. And with Yuuichi's luck, he just happens to find out he's not just the ''Key'' for one of the HiMEs, but for two... Two highly competitive, rival schoolgirls. And that's only the start of the trouble.

Kakusho Bizarre adventures in the world

Marriage Royale's story revolves around the male protagonist, a high school student named Tsukasa Hinomoto, who is told one day by his parents that he was adopted. Furthermore, they tell him that his real father is a manager of a large company, meaning he is very rich and holds a lot of power.

Tsukasa's real father wants his son to marry a good woman, so he sets up an event known as Marriage Royale. Beautiful girls from all over Japan will come together at a school built especially for this event and vie to become Tsukasa's fiancé.

The school is located on an isolated island near Japan, and Tsukasa himself is taken there to live in a mansion in the care of two twin maids: Miku, the elder sister, and Miu, the younger.

From Intercross:

Ouri is a girl who dreams of getting married to someone who will protect her, just like her dad protected her mom. When she refuses an arranged betrothal to someone she doesn't know, her mom insists she attends Clover Academy, where there are plenty of fiancee candidates. Rumors about her quickly spread around the school, causing many boys to swarm around her.

Then, caught in a pinch, she's suddenly rescued by a "Meteorite Guardian" named Knight, who is now contracted to Ouri to protect her...

Ultra sensitive body doesn't listen anymore!!! The game(?) of robbing and being robbed between rich presidents family which owns a sensitive body and the poor people which only has body begins!

Orginal webcomic

From Syuura:

During a field trip to the imperial capital, Tokyo, Kaga Nanao overhears the beautiful melody of a violin and immediately becomes captivated by it. In order to meet the mystery violinist, Nanao learns the violin and defies her father's wishes by attending the Marianne Music Academy for girls in Tokyo. Upon arriving at the school, Nanao comes across her mystery violinist who turns out to be Sagami Takenomaru, the violin prodigy and adopted son of the famous violinist, Sagami Chougo-sensei. However, Takenomaru isn't just a regular person, he's determined to complete a mission and fulfill a contract...

Note: "Naki Shoujo no Tame no Pavane" means "Pavane for a Dead Girl" and is a wordplay on the Japanese translation of a solo piano piece, written by French composer Maurice Ravel in 1899, called "Pavane pour une infante défunte" - Naki Ōjo no Tame no Pavane or Pavane for a Dead Princess.

From Divine Sanctuary:

Lilith is a phantom thief who is after genius artist, Michelle Corradi’s portrait. After she had already stolen some pictures, Michelle had the idea to catch her. When she announces to steal his new artwork he met her and fell in love with her. What will he do to meet her again..?

Kouta's school-year is off to a great start; this year he and lovely Ayano are in the same class—and they're sitting next to each other! Here's the problem: whenever Kouta gets excited he passes out—and wakes up in a stuffed toy. (No, he's not cosplaying—he is the stuffed toy.) It's never the same toy and it always seems to have some sexy girl hugging it close. Then his childhood friend Ako gets involved and Kouta begins to realize Ako is not a child anymore...

The story of Fukumaden takes place in a world after the Demon King has been defeated by the hero. The hero makes a harem of women to pass down his blood, because the Demon King is fated to return in the next few hundred years. However, because he gathered too many girls, there are 100 women in waiting. The story depicts the women spending their time talking amongst each other as they wait for their turn to meet the hero.

Alcohol turn the timid guy into a bad boy? The story about the life of a guesthouse owner.