The White Queen or The 100 Worlds. 18

Romance

Her whole life has changed in a moment when she said 'Yes'

Solo Leveling

Action Adventure Fantasy

Ten years ago, after "the Gate" that connected the real world with the monster world opened, some of the ordinary, everyday people received the power to hunt monsters within the Gate. They are known as "Hunters." However, not all Hunters are powerful. My name is Sung Jin-Woo, an E-rank Hunter. I'm someone who has to risk his life in the lowliest of dungeons, the "World's Weakest." Having no skills whatsoever to display, I barely earned the required money by fighting in low-leveled dungeons... at least until I found a hidden dungeon with the hardest difficulty within the D-rank dungeons! In the end, as I was accepting death, I suddenly received a strange power, a quest log that only I could see, a secret to leveling up that only I know about! If I trained in accordance with my quests and hunted monsters, my level would rise. Changing from the weakest Hunter to the strongest S-rank Hunter! (Source: Kakao, translated)

Solo Sex

Romance Yaoi

Though he's a High School senior, Takitani works as an escort named Ryou. To escape being caught, Takitani does his best to remain inconspicuous in school. But one day a classmate suddenly shows up as his customer. The son of a doctor, Kunimi is a total prick who's always picking on Takitani. Anxious not to be caught, Kunimi is completely oblivios to Takitani's disguise and becomes smitten with his cute and cool attitude. Takitani tries to push him away so they don't become too intimate, however... [from Baka-Updates]

Raiden-18

Action Comedy Seinen

Taking a break from her popular, brilliant, Fullmetal Alchemist; Arakawa-sensei drew up a one-chapter humorous Shounen story about a Frankenstein tournament, for mangazine GX to commerate their 5th year anniversary. (Source: Anime-Source)

Futari Solo Camp

Slice of Life Seinen

Gen Kinokura loves camping solo. He enjoys the quiet solitude away from the hustle and bustle of the city, and being able to appreciate nature all by himself. But on one camping trip, his solitude is broken by the appearance of Shizuku Kusano, a young woman who wanted to camp solo herself, but is ill-prepared and completely out of her league. While he tries to to get her to go home so he can camp in peace, she refuses, and stubbornly insists on accompanying him on future camping trips until she's ready to camp solo. Thus Gen and Shizuku's days of solo camping together begin. [Written by Denji]

18 Diary

Romance School Shoujo

1. 18diary 2. 17's Bible 3. Tadashii Hoshi no Miagekata

Durarara!! 18 Shiryaku

Action Drama Supernatural

A series of side stories that were bundled with the first press release of all 18 Blu-ray/DVD volumes of the 2nd season of the anime.

Ojamajo Doremi 18

Magic School

18-sai no Kodou

Shoujo

Another tender love story which fails to run smoothly from the master of such works Yukari Kawachi! This is a one volume "novel" type manga. Rui will be a model, and Tougo will be a painter—the two young childhood friends dream about their future. When Rui's father dies when she is 17, she goes to Tokyo, to fulfill her dreams—and meets a handsome make-up artist and...! (Source: Hidoi~! Translators)

18-sai no Himitsu

Romance School Shoujo

18-year-old Sako is tired of her loveless high school life. Her only comfort is her teacher whom she frequently visits for love advices. Now that her graduation is coming up, will she be able to seize the love that she has always wanted?

R-18 Love Report!

Romance School Shoujo

Riko Mitsumi is sixteen year-old girl who is pretty and a good student. She would be like most girls if she wasn't constantly dreaming about sex and using a pseudonym to write about it. (Source: M-U)

Bronze: The Final Chapter

Drama Shounen Ai Yaoi

Picking up where volume 14 of Bronze left off, this is an epilogue to Koji and Takuto's story. Includes side stories and epilogues for Koji's brothers, as well.

Captain Tsubasa Pilot Chapter

Shounen Sports

This was the root of everything, the debut work of Takahashi sensei, a nostalgic memory. The story of Genzo Wakabayashi and a boy named Tsubasa Taro.

Nanami 18-sai Mama ni Narimashita

Yaoi

Nanami's older sister ran away from a member of a Japanese mafia; therefore, even though Nanami is only a 18-year-old boy, he has to be the mother of the baby and a captive.

Ginga Nagareboshi Gin - Special Chapter

Adventure Seinen

A spin-off story about the Kai brothers' puppyhood.

18 Years Old, We Got Married

Shoujo

Life isn't that great when it's composed of a stubborn sister, single mom, and a dad that left you for someone else? If that's not enough, you meet a dwarf that's part of a famous boy band? Could this get any worse?! (Source: Within Silence)