Kawaii Kara Kimi Ga Warui
Taiki x Yukito - Yukito is an average high school student with a gorgeous and outstanding twin sister, whose only similarity she shares with him is her face. Yukito, who's always getting compared to his sister, also has someone he likes - that person being his cousin, Taiki. There are rumors of the cool and popular Taiki and Yukito's sister liking each other. The relationship between Taiki and Yukito had become one where they'd both grown reserved around another, but using the preparations for the school festival as an opportunity, Yukito and Taiki both quickly grow close again! Yukito's heart wouldn't stop racing after being saved by Taiki when he was being troubled...! Moreover, in an unexpected turn of events, the two of them started sharing ""a secret""...? - First time I've ever wanted to punch the ML. I wanted him to suffer more and for Yuki to not forgive him easily - "I really want to slap Taiki ???? Seriously, wtf is wrong with him and him thinking that saying to a person he supposedly likes that they’re just a replacement for their sibling?!?? What frustrates me more, too, is that he never throughly apologized for what he did to Yuki. And the fact that Yuki so quickly accepted things being the complete opposite of what he had been told to believe is just dumbfounding."
Houtou Musuko to Koi no Ana