The doctor that is in charge of Rika's care. He used to take care of her at another hospital but was transferred to the one in Yūichi's town. Rika then transferred to the same hospital so that he could still be her physician. He harbors some feelings for Rika and he tries to sabotage Rika and Yūichi's relationship claiming its for fun. In reality, Natsume is doing this out of his own experience with his wife who died from a similar condition to that of Rika and possibly doesn't want Yūichi to go through the same thing.  -Wikipedia

After contracting hepatitis A, Ezaki Yuuichi has been confined to a hospital away from his friends and family, much to his displeasure. To relieve his boredom, he has taken to sneaking out of the hospital, usually putting himself on the receiving end of a beating from his nurse. Upon meeting a girl his age also staying in the hospital, he is immediately captivated by her beauty. Akiba Rika's personality is not quite as captivating as her beauty however. In fact, she is rather selfish, moody, and bossy. But as the two spend more time with each other, they become closer, sharing the ordinary joys and trials of a budding teenage romance, even when darkened with impending tragedy - for Rika's condition does not leave her much longer to live.<br><br>
[Written by MAL Rewrite]

The story of Hantsuki focuses on the budding relationship between the seventeen years old Y&#363;ichi Ezaki and Rika Akiba. Both are hospitalized in Y&#363;ichi's home town for their respective conditions. Y&#363;ichi has hepatitis A, while Rika has problems with a weak heart valve. These teens would then fall in love while they spend time with one another. The story is based in Ise, Mie prefecture as implied by the "Welcome to Ise" sign shown after the opening sequence in the first episode of the anime series.

During the winter, Yuichi was hospitalized due to hepatitis. Randomly he would try to escape from the hospital but would get beat up by the nurse. One day, he happened to meet Rika, a girl of his age, in the next building. He was fascinated by her beauty, but she was very selfish girl. Although she led him by the nose, he began to be attracted by her. However, when Rika told him about her illness, he knew why she acted so selfish; she didn't have long to live.

Gorou Natsume