Saeki Nozomi is a nurse that works at the hospital where her cousin is stay at due to a illness. At this time in the story, she is married but by herself while her husband is on business trip. She is also a bit horny as her period is coming up but tries to be faith to her husband and only flirts with her cousin whom she considers as her little brother. - Yumi is the guy's sister who also works at the hospital as a trainee since she is studying to be a nurse as well. She has strong feelings for her brother and worries about him a lot but doesn't cross that line...

(Source: Anime News Network)