You Don't Need to Say 'I Love You' to Family

I, Shirogane Tsuki, am a sickly genius boy who could kick the bucket at any moment. My only comfort is my older sister, who depends on me in an unhealthy way and sees me as her whole world. Her almost twisted control over me is something I've encouraged myself. After all, with my frail body, I can only truly feel alive when she needs me. I thought my days would simply wind down to their end... until one day, my parents told me I had a fiancée. And just like that, my peaceful life was over. My childhood friend Nanami Hiromachi is a terrifying genius pretending to be an ordinary person. Another childhood friend, Rui Yashio, is an obsessive girl who'll do anything to achieve her goals. Even the members of the idol band I manage, and the meticulous guitarist in my sister's band... have started looking at me strangely...