Imouto ni Kiite Minai to

Daichi Fukumori is just beginning his second year of high school when a harmless fabrication threatens to unravel his daily life. Hoping to build a connection with the girl he has a crush on, he invents a story about having a younger sister, using the fictional sibling as common ground to spark conversations. However, carrying the weight of this deception eventually takes its toll, prompting Daichi to finally gather the courage to confess the truth and come clean about his lie. Before he can set the record straight, his world is turned upside down by the sudden arrival of a mysterious girl who confidently calls him "big brother." To his absolute astonishment, the imaginary sibling he fabricated has somehow materialized into reality. While the shock of discovering that his lie was no longer a lie leaves him reeling, this bizarre twist is only the beginning of his troubles. An even more outrageous and chaotic situation quickly unfolds around him, escalating far beyond anything he could have anticipated. With events spiraling dangerously out of control, Daichi realizes he must urgently sit down and have a serious conversation with his unexpected new sister before his entire life descends into complete madness.