Sono Yubi De Hagashite
Boy that is constantly being sexually abused by his uncle at home, bullied and physically abused by his classmates in school, and most likely blackmailed by his teachers, finds solace in a dark and lonely student-teacher who more than anything craves for acknowledgement. The story is really, really sad; that poor child has lived a miserable life for who-knows-how-long. Things seem to fare slightly better with this dude, but still, the relationship doesn't seem very healthy at all. Not that anyone reads manga for the healthy relationships :P
Seven Days
Freshman behaves like the perfect boyfriend for exactly one week, if he hasn't fallen in love with that person by then, he breaks up with them and deletes their contact information. Despite all that, none of his exes will say anything bad about him. Curious about what was so special about him, Senior that is widely popular, but whom all girls have broken up with him saying he disappointed them, decides to ask him out. Very interesting premise, as usual the art is just absolutely gorgeous. Couldn't help but love both characters.
Mei no Maiden
Maidens, a half-casino-half-brothel that mixes gambling with money and sex, currently employs the Iron Maiden, an undefeated call girl. She is assigned as the mentor to the new girl,who happens to be quite innocent herself.
Unordinary
https://www.webtoons.com/en/fantasy/unordinary/list?title_no=679
Kainushi wa Akuma
Woman ostracised because of her bright red hair, is saved by a priest who happens to be a truly powerful demon working for the Vatican. Because she was so hated in her village she decided to accompany the priest, since after the incident only his blood can keep her alive. Out in the world, she seems to catch everyone's eyes for her bright red hair and her beautiful green jade eyes, the demon priest tells her that her eyes have special powers that can heal but also attract evil beings; more and more she's being protected by the priest, who seems to be very interested in her and ends up making her his "pet". Girl's a heavy tsundere, the plot always seems to rely heavily on the fact that people are attracted to her and the demon priest is so powerful, there is very little character development, to the point that a side character seems to grow more than the two leads. In a world where it seems most people are quite beautiful, the ones that are supposed to stand out as "the most beautiful anyone has ever seen" really look ordinary.
Sarashi Asobi
Main story is about a grim reaper that becomes enchanted by an infinitely kind human, the very one whose soul he was supposed to recollect. After spending time with her, he decided he'll do everything in his power to keep her from Death's door. I had read some comments about how the "last chapter was too sad" and I spent way too much time attempting (but failing) to prepare my heart for the sad to come. - Fortunately it wasn't that story that had that. The second story (and a one-shot, fortunately) is about an exorcist who, out of kindness, ends up helping out a succubus that doesn't want to behave like other succubi. Happy that her powers had no effect on him, she agreed to marry him, unaware that every kiss they had fed his soul into her.
Tales of the Kingdom
First chapter is the full story of http://www.mangago.me/read-manga/adolte_and_adarte/ I had only seen the first half of this story, I'm so glad that there was a continuation! Oh but... it's so sad... Ardolte must've lived pretty miserably after Ardalte left. Kinda wish Ardalte Sr., would've decided to stick and help Ardalte Jr., now that his "dad" was gone. The following chapters (2 and 3) are about a King and his aide, and then about the aide's past life (chapter 6 - onwards). Part of the King and his Aide's story is in http://www.mangago.me/read-manga/the_king_and_the_attendant/ This book should be renamed Sad Stories About Twins xD
Velvet Going Underground
So many stories, this book compiles two other books (and a handful of other related stories) so that you can read everything in one go. I discovered that many of those stories were actually connected to other ones, I was quite pleased. Also, many of the stories here seemed to be sort of like a dark take on famous fairy tales, I loved that.
Under the Skin (KUSABI Keri)