Kyougoku Ka No Kekkon summary:

Enter into a fake marriage with me! Seishiro Kyogoku, who works as a secretary for his father, the minister of Justice, is panicking. He has to live secretly with his half-brother, Reo, who suddenly appeared! Not only that, when he met his former classmate, Takeru Kyogoku, by chance, he discovered Seishiro’s secret! Seishiro declares that he will protect Reo and Takeru with his life, while Takeru says he will help Seishiro as long as he can have sex with him… Can love be born from lies?