"Unsentimental" is Chapter 43 of Tsurezure Children. It is centred around Fuyumi Toda and Yoshiharu Sunagawa.
Yoshiharu confesses that he might like Fuyumi. Fuyumi, confused, asks what he means by 'might'. Yoshiharu clarifies that he had never fallen for someone, so he doesn't know. He then follows up by asking if Fuyumi likes him, to which she replies "If I have to chose, then yeah, I guess." Yoshiharu then asks if they want to go out, with Fuyumi answering "Whatever." Fuyumi then says she doesn't mind if they do or don't date. Yoshiharu asks to decide on which one. Fuyumi then says no, but Yoshiharu asks why, if they both like each other. Fuuyumi, surprised at the question, questions if he wants to date her that badly. With much thought. Yoshiharu reluctantly replies with no.
Adding to that, Yoshiharu just doesn't like the idea of Fuyumi going out with another guy, and asks if Fuyumi is the same. Fuyumi shrugs a yes. Yoshiharu asks once again if they are dating, and Fuyumi half-heartedly says yes.