Sayonara Women

(from ebookjapan):
A high school girl, Mari, aspires to be a mangaka. By chance, she becomes friends with a math teacher who used to be a model for her manga, and begins to fall in love with him... but what happens?　A collection of short stories with faint feelings!

Note: Digitized Hakusensha bunko release contains an afterword from Ooshima and 4 other one-shots, including the title one-shot of Shinjirare Nation.