After falling ill due to a kind act of lending his umbrella to a girl in need, Amane Fujimiya anticipates a simple return of the borrowed item. Unexpectedly, Mahiru Shiina, known as the 'Angel' at Amane's school and his neighbor, goes above and beyond. Rather than just returning the umbrella, she insists on aiding his recovery from the cold. Unaware of the chaos in Amane's apartment, Mahiru bluntly labels it 'unsightly.' Despite her harsh assessment, she persists in helping the hapless Amane. Otonari no Tenshi-sama ni Itsunomanika Dame Ningen ni Sareteita Ken chronicles Amane's care under Mahiru, who tackles various tasks, from tidying up his place to preparing meals. Is there any limit to the Angel's capabilities?