Boku no Shiru Anata no Hanashi
Chapters 1-3: High schooler Haato feels a bond with his abusive mother's former lover Shibusawa, a member of the yakuza and the only person to have shown him kindness. Years later, Haato is working as a host and is openly in love with Shibusawa, who toes the line of a relationship but never crosses it until Haato loses someone close to him. The last story is about two coworkers: a man confesses to a coworker he sees feeding stray cats outside their building. ETA June 2020: After rereading the first story for the billionth time, I bought the manga. Hisashi does marry, but his husband dies post-story. We pick him back up here when he is 39 (chapter 5): https://www.mangago.me/read-manga/akanai_tobira/ July 2021: this might be the story I’ve read the most. Even more than the one about the hot dad who gets back together with his boyfriend after 20 years. Something about this makes me feel so sad and so moved. I wish there were more than just three chapters. I would love to know more about their daily life after they lived together.
Joushi To Ore No Himitsu
Years after a drunken one-night stand, Hiroki is shocked to find his new boss, Kurosawa, is the man who'd found and comforted him in the wake of his father's death. Hiroki doesn't expect to be recognized; he's since reinvented his image in order to pay off his father's debts, but Kurosawa knows him immediately and confesses that he's been searching for Hiroki for the past four years. Overall an enjoyable story, although there is an immature test of Hiroki's motives for being in the relationship that could've been settled with a frank conversation, and the ending is a bit rushed.
Konbini-kun
Endou left middle school when his crush on a classmate made him a target of bullies. A year later, he begins work in his uncle's convenience store, where he meets Kouhei, a fellow 16-year-old who quickly goes from intimidating co-worker to close friend after they rescue a kitten. Rather than risk his only remaining friendship, Endou remains closeted about his past and sexuality, but his newfound stability seems on the verge of collapse when his former schoolmates discover where he works, and Endou comes face to face with the boy he had once loved. This story largely deals with bullying and its long-term emotional fallout; the romance is secondary to Endou's own healing and self acceptance. Above all, it is their friendship and Kouhei's insistence that there's nothing wrong with Endou or his past feelings that are the heart of this story.
Goodbye Lilac
A sensitive, well-paced, beautifully drawn story of Katou, a boy inspired by his teacher, who grows up to become a teacher as well. Five years after graduating, they reunite as coworkers, and Katou is still in love.
Takashima Kouichirou no Risou no Koibito
A narcissist agrees to be sex friends with an impotent co-worker in exchange for that co-worker's silence about having a selfie as his lock screen.
Bi no Isu
Explicit, disturbing yakuza love story. I liked the couple a lot and it was nice to see their love develop. A man struggling with ED goes to a specialist...who turns out to be the childhood friend he used to hook up with, whom he blames for his impotence, and then has sex with in the office. PWP. Coworkers hook up after realizing their years-long mutual interest, and then they have breakfast! Features the wonderful "of course you're not still here in the morning, I was an idiot to get my hopes up, but oh! you were just out buying groceries!" trope.
Kimi Ga Koi Ni Oboreru
After being turned down by a childhood friend, Rei falls for a senior employee at his parents' store. Be advised there is on-page dubcon (I read it as noncon, to be perfectly honest) twice.
Ore To Joushi No Kakushikoto
A selfish boss and his subordinate end up in a hotel because the trains have stopped running. The boss, too drunk to recognize his coworker, comes onto him and asks his subordinate to film the encounter, giving him the perfect weapon for revenge. Only the more they get to really properly know one another, little by little, their relationship begins to change. I almost skipped this and am so happy I didn't. This was a fantastic love story, well paced and believable. I agree with other commenters who said this has the best confession scene they've ever read!
Eigyou Nika! Dj - Kiss Me
Ayamu and Seiji find it hard not to jump each other at the office.
Konna Nichijou