Torawareta Amai Kemono-Tachi
A company's future president is in a relationship with his long-time tutor Chiharu - a possessive, emotional man who is so afraid Kazuki will leave him, he takes him to a cabin and slaps a chain on his ankle for a few days. Not the healthiest relationship - I wouldn't recommend anyone DO this - but it's fiction and they're really into each other.
Hitorijime Theory
A collection of stories about a series of couples. This is the one with the guys who had lived together for two years and even slept in the same bed before they ever hooked up.
Hanagaya Eigyousho No Kare
To escape a confession from a clingy coworker, a man asks out his older boss - a charming guy known for turning everyone down - and is shocked when he accepts.
Ren'ai Shinan!
A graphic designer helps his hopeless boss improve his looks so he can attract women, but (you'll be shocked, prepare yourself) his boss falls for him instead. But the designer isn't interested in a relationship and there is some sad pining.
Romanticer's High
Two coworkers who don't get along hit it off over drinks and end up kissing, but when one brushes it off as drunken antics, he hurts the other. A guy who can't keep a job is semi-stalked by a wealthy guy who gives him bizarre gifts. There were others which I have forgotten.
Baked Sweet Glasses