GuessAnime.

10. Flat

Heisuke is a young man who was left in charge of taking care of his little cousin Aki for a day. Being an only child who usually stays at home alone, Aki is quiet, reserved, and will go out of his way not to make trouble for others. As they spend more time together, Aki begins to grow very attached to Heisuke, especially since Heisuke's hobby is to make sweets and desserts. The quiet Aki eventually opens up to Heisuke, and Heisuke in return teaches Aki that sometimes it's all right to be selfish and say what you really want to do.

Flat is finished and has 8 Volumes and 40 Chapters. It is also Known as: flat, Fuyume, Winter Sprouts

9. Ouran Koukou Host Club

Haruhi sticks out like a sore thumb as a poor, smart girl who got into the hoity-toity Ouran High School on talent alone. When she mistakenly wanders into the meeting room of the host club and breaks a valuable vase, she's recruited to join the club. Realistic and sarcastic, Haruhi isn't used to being around crazy people like the princely Tamaki, scheming Kyouya, silent Mori, immature Hunny, and devilish Hikaru and Kaoru, but she's got no choice if she ever wants to pay earn what she owes. Too bad the club is made for girls to come and be entertained by gorgeous guys -- and Haruhi's been mistaken for a boy!

Includes chapters of the story "Romantic Egoist" in various volumes, starring a pair of twins who play matchmaker with their fellow students, teachers and the like.

Note: The final volume contains a special bonus chapter where the group travels to Spain.

Ouran High School Host Club is finished and has 18 Volumes and 87 Chapters. It is also Known as: 桜蘭高校ホスト部, OHSHC, Romantic Egoist

8. 14-sai no Koi

A story about two unusually mature young people. They are both smart, very together and they are in love. But, as grown-up as they act, they are still just 14 and their feelings for each other are captured with tenderness and lack of nostalgia, but very cutely.

Love at Fourteen is finished and has 12 Volumes and 143 Chapters. It is also Known as: 14歳の恋, 14-sai no Koi

7. Nijiiro Days

Nijiiro Days follows the daily lives of four high school boys: the hopeless romantic Natsuki Hashiba, the sadist Keiichi Katakura, the playboy Tomoya Matsunaga, and the smart otaku Tsuyoshi Naoe. Even while constantly struggling in their studies, they spend their days goofing around and having romantic misadventures.

On Christmas Eve, however, Natsuki is dumped by his girlfriend. While crying alone, he receives a pack of tissues from a girl wearing a Santa Claus costume, and, in return, gives her the scarf originally meant for his ex-girlfriend. As the holidays end and Natsuki returns to school, he finds out that the girl is named Anna Kobayakawa—who luckily goes to the same school as him! Having fallen in love with Anna, Natsuki aims to get closer to her, despite his friends interfering with his plans.

Included one-shots:

Volume 1: Aru Toshi to Sorekara no Watashitachi

Volume 5: Shinbun-bu no Yoriko-kun

Rainbow Days is finished and has 16 Volumes and 80 Chapters. It is also Known as: 虹色デイズ, Aru Toshi to Sorekara no Watashitachi, Shinbun-bu no Yoriko-kun

6. Fuudanjuku Monogatari

Volume of stories about the members of Fudanjuku, with one chapter focusing on one specific member at a time.

Fuudanjuku Monogatari is finished and has 1 Volumes and 7 Chapters. It is also Known as: 風男塾物語, The Fudanjyuku Stories, Fudanjuku Monogatari

5. Horimiya

At school, Kyouko Hori is known for being smart, attractive, and popular. On the other hand, her classmate, the boring, gloomy Izumi Miyamura tends to get painted as a "loser fanboy." But when a liberally pierced and tattooed Miyamura appears unexpectedly on the doorstep of secretly plain-Jane homebody Hori, these two similarly dissimilar teenagers discover that there are multiple sides to every story...and person!

Notes:

-Includes 20 extra chapters.

-The 17th volume got released on July 18, 2023. This was 2 years after its original ending. This new volume included 10 extra chapters.

Note: Chapter count includes 20 extra chapters.

Horimiya is finished and has 17 Volumes and 152 Chapters. It is also Known as: ホリミヤ, Horimiya

4. Koko wa Green Wood

It seems like 15-year-old Kazuya Hasukawa's life can't get much worse. Not only did his older brother marry Kazuya's first love, he brought his bride home to live with the family! Forced out of his own home, Kazuya enters an exclusive all-male boarding school, Ryokuto Academy. Unfortunately, a prestigious education is little compensation for getting stuck with the cross-dressing roommate from Hell...

Here is Greenwood is finished and has 9 Volumes and 60 Chapters. It is also Known as: ここはグリーン・ウッド, Koko wa Green Wood

3. Ame Nochi Hare

Amagai Gakuen, a prestigious school for boys, was hit by an unusual spring storm during the entrance ceremony. Four boys - Hazuki, Toma, Yusuke, and Junta - were all caught in the storm's violence and were affected by a strange phenomenon. All of them were transformed into girls!!

Inevitably they will meet someone and fall in love. Bikke wholeheartedly introduces this new, beautifully drawn series about boys and girls coming of age.

Ame Nochi Hare is finished and has 0 Volumes and 39 Chapters. It is also Known as: あめのちはれ, Ame Nochi Hare

2. Danshi Koukousei no Nichijou

Follows the daily experiences of high school boys.

Danshi Koukousei no Nichijou is finished and has 7 Volumes and 132 Chapters. It is also Known as: 男子高校生の日常, Joshikousei wa Ijou