This is a short but sweet manga, with several unexpected plot developments that kept me intrigued.
I think one of the most erotic types of story you can tell involve two people both wanting to have sex, but not being able to for whatever reason--it creates a great buildup of tension of desire and action. This manga pulls this off beautifully, having Subaru lose her self-control for an hour a day and beg Akira for intercourse. And though he wants it as well, he struggles with the ethics of it, especially since Subaru would be pissed at him if he took advantage of her time of weakness. It deals with the importance of sobriety in consent.
The manga also deals with social expectations and how people have multiple personas and roles they play depending on who they're interacting with. Subaru, even with self-control, acts differently with her classmates, with her sister, with Akira at school, and with Akira in private. It also deals with the negativity put onto having sexual urges and implies that sexual "purity" shouldn't be seen as more virtuous, that everybody has urges and shouldn't have to feel ashamed of them.
The world felt pretty insular--largely only focusing on the two main characters in one room. While there are several scenes in classrooms, the other students never rise above being background characters. Some of Subaru's family is introduced, but Akira's family is never seen or even talked about, beyond being poor. Perhaps the story was best served by focusing entirely on Subaru and Akira's love story, but I found the most fascinating scenes to be when Subaru lost control around people other than Akira (and reacted in ways other than horniness), so I would have loved to see the story expand and open itself to including more varied scenes of loss of self-control.