I think it's a yaoi that has multiple short stories but in one of the stories it involves a high school student and a teacher ( maybe already married) who are in a romantic relationship and the student is kind of crazy and wants to monopolize the teacher and have him all to himself that he sends pictures of them having sex throughout the school getting the teacher fired, after the teacher leaves I think like a day or two passes by and the student goes to the teachers apartment and the teacher looks exhausted and malnourished with a big mess in his apartment and he looks at the student and he's like oh you're still here I thought you would have left me too and says at least I still have you