Manga Like Futago Matomete "Kanojo" ni Shinai?

Chikage is a beautiful girl in my class who is smart and well-behaved. She is my rival in school, but after school, she has another face. After school, she plays in the arcade with an innocent smile that would be unimaginable in class. I try to make friends with Chikage on campus and play with her after school in order to get to know her better. It seems like we're getting closer to each other, until finally… Chikage confesses her feelings for me as we were leaving school! I decide to accept her confession and I tell her how I feel on our way home from the arcade. Just when I think Chikage is now my girlfriend, another girlfriend shows up! (Source: Fantasia Bunko, translated)