We can't be childhood friends anymore

https://mechacomic.jp/books/230219 "I'll become your boyfriend, Minami." High schooler Minami Kayano is deeply in love with her childhood friend, Kei Ichigaya. However, fearing it might ruin their relationship, she keeps her feelings to herself. One day, a senior at school named Ide confesses his feelings to her. Although she politely declines, she unfortunately begins to experience stalker-like behavior from him. While in a deserted area, the senior grabs her arm, putting her in a difficult situation. Suddenly, Kei arrives to help, saying, "What are you doing to my girlfriend?" To protect her, Kei begins acting as her boyfriend. Even though it is supposed to be a fake relationship, he starts acting more boldly, telling her, "You should be more aware that you're my girlfriend." Will their relationship as childhood friends undergo a major change? A heart-pounding secret relationship with her childhood friend begins!