夏なつへの扉とびらMeanings1nounThe Door into Summerwork of art, literature, music, etc.Title of a 1957 science fiction novel by Robert A. Heinlein. Used as a proper noun.「夏なつへの扉とびら」はロバート・A・ハインラインのSF小しょう説せつです。"The Door into Summer" is a science fiction novel by Robert A. Heinlein.