Closet ni Ohoshi-sama

When Sei is stressed, it manifests through a mark that spreads like petals across his neck. He spends his days hiding behind discreet glasses and a suit that covers his neck. He is in love with Abu, a designer working for one of his client companies. Unlike him, who hides his homosexuality, Abu is openly gay and seductive. One evening, while going to a bar to relieve his stress, he runs into Abu! Circumstances force him to reveal the cause of the bruise on his neck. "Shall we have sex to see if it makes it disappear?" At Abu's kind suggestion, a romantic relationship begins!

(Source: Tokuma Shoten, translated)