오늘부터 동거 1일차 is a mobile dating simulation game developed by atticfriends Inc. In this game, players take on the role of Yu-jin, a typical college student with no prior dating experience, who suddenly finds himself waking up to a girlfriend one day. Thus begins a sweet cohabitation life, as per her request.

Aside from following the story, players can also experience various elements such as going on dates, working part-time jobs, and going out. While enjoying the delightful experience of gradually building up Serin's affection, there is a constant sense of unease, the protagonist's own worries, and even major crises in the relationship.

Can you navigate through this relationship, feeling both happiness and excitement, and successfully continue this love story with her?