Yona Yona Bokura wa Machiawase

Kou Nishito, a graduate student suffering from insomnia, and Yoiko Ichijo, who has been unable to sleep due to loneliness since becoming independent, are discovered to be "compatible" individuals with a highly compatible sleep gene, "Nemunoki." They begin a cohabitation experiment to achieve stable sleep. Though hesitant, they fall asleep in the same bed, and drift into a deep sleep they haven't experienced in years... The feeling of having someone beside you. The curtain rises on a strange and heartwarming story of two awkward people. (Source: Kadokawa, translated)