Adult Problems

After salary-man Saki Hiroyasu faints due to a fever, college student Shinomiya Jun takes care of him for two days. Saki repays him in an interesting way and they soon become one of the cutest couples in Yaoi. Jun, who's 18, is the cutest, fluffiest and most innocent ukes in Yaoi. You just want to pet him and take him home. Mature, 33 year old Saki falls head over heels for the adorable Jun. (15 year age gap)

Shinya Kaito’s planned to elope with his lover Yuriko but she was married off to a powerful man named Sugai. He swore to get revenge. 18 years later Sugai Nanami, her son, is bought by Kaito and used as her substitute. Considering Kaito was originally in love with Nanami's mother, he's 18+ years older than Nanami.

Yuki needs money to purchase the medicine that could save his brother’s life, so he decides to sell himself in a pet auction. Before the auction his friends Masashi and Ryuu prepare him. Ryuu is 12 years older than Yuki.

Lawyer Matsuno Shuuichi wakes up after a night of drinking to find that Sakura Rin, a male prostitute, had spent the night. After inviting him to live with him, both start developing feelings for each other. Rin is 18 and while Matsuno's age isn't mentioned he's got to be at least in his late 20's.

Cute story about how Arima Kouhei, a fudanshi, and his little brother Kanata fall in love with a hairdresser and a teacher respectively. Their ages aren't mentioned but I'm pretty sure it has to be more than 5 years.

Tokura Ei is a forensic archaeologist who’s dealt with discrimination due to the fact that he’s gay. He struggles to keep his distance from his childhood friend and lover Kamiryou Gin, because he doesn’t want Gin to experience bigotry. Ei and Gin are exactly 7 years apart.

The manga includes the story of a businessman who falls in love with his manager, who happens to be a fortuneteller; the story of a student in a relationship with his teacher, who's a sex beast; and the story of a businessman who gets topped by his subordinate, who's a sadist. The last couple has an age gap of 7 years and in the second couple between a teacher and his student there has to be at least 5 years in age difference.

Jinnou Shirou loves rabbits, the only problem is that his stern expression scares the rabbits away. One day meets Kou, a rabbit café worker/struggling university student and Jinnou finally gets to pet a bunny. But Jinnou has taken an interest in Kou, who to Jinnou, resembles a rabbit. I'm pretty sure between college student Kou and 29 year old Jinnou there's at least a 5 year gap.