You clicked meaning u wanna know what happens. not going into details but basically they argue. Then sis kisses MC and childhood friend gets mad. sis leaves, leaving behind MC and childhood friend. Childhood friend basically tells MC that she cant trust him and then leaves. MC goes home, enters sis room. There she apologies and says other things. Her face become blushed that the MC (in his mind) calls her cute. "With her cheeks dyed scarlet red, and fleeting smile, she was more beautiful and captivating than any other girl I had ever seen." He then hugs her and as he sees her shelf, he sees she has one of his novels. A week passes since the incident, he meets up with someone who helps him on his novels. There they talk about an author whos the same age as MC and writes good. Apparently her work involves childhood romance and guess what's the name of the character in the novel..... yup it's Riiko. hmm that sounds familiar. So basically, his sister’s a super fan of his work and we can infer that his rival author is his childhood friend Rinko.