Onzoushi-kun no Konyaku Jijou

Ranzan Kazuomi is living a typical university life, despite secretly being the heir to a top domestic corporation. His days are filled with drinking with friends and attending mixers, but things take a turn when he is pressured into an arranged marriage with Houshubana Chitose, a handsome and hyper-competent childhood friend from a rival company. Though Kazuomi has always felt intimidated by Chitose's brilliance, he reluctantly agrees to a temporary engagement to appease their families while his older brother, who opposes inheriting the company, works to convince their parents otherwise. Keeping their engagement a secret, the two begin living together under the pretense of being merely roommates. However, during a party, Kazuomi accidentally consumes a drink spiked with an aphrodisiac. When Chitose comes to his rescue, he publicly declares Kazuomi as his fiancé. At first, Kazuomi assumes it’s a ploy to save him, but he’s left reeling when Chitose passionately confesses, “I want you to be my real fiancé.” The confession is sealed with a kiss so sweet it leaves Kazuomi weak at the knees—and questioning everything. (Source: Gentosha, translated) Note: Includes one extra chapter.