Monogatary.com (stylized in all lowercase) is a social networking service website, owned by Japanese entertainment conglomerate Sony Music Entertainment Japan and launched by Yohei Yashiro on October 30, 2017. The website focuses on creative writing and illustration, where users can submit works based on a daily updated theme. Monogatary.com is best known for its fictional stories that have become sources for duo Yoasobi's numerous songs.
In 2014, Sony Music Marketing (now Sony Music Solutions), a subsidiary of Sony Music Entertainment Japan, had the idea of creating a creative writing submission website. Despite internal positive reception, the idea did not align with the company's primary focus on music marketing. A year later, as the SMEJ business program EnterLab launched, SMM's then-supervisor suggested Yohei Yashiro, who previously helped on the unsuccessful project, to resume the creative writing submission website. Yashiro launched Monogatary.com on October 30, 2017. It takes name for Japanese word , meaning "story".
Unlike most novel submission websites, Monogatary.com will give users a theme daily to contribute any creative writing and illustration. Furthermore it also incorporates social network service features. Since 2018, Monogatary.com has hosted an annual fiction contest, titled Monocon, divided into various categories and awards each year. The works submitted on the website have been adapted into books, audiobooks, anime series, films, games, or songs with accompanying music videos.
In 2019, Yoasobi, consisting of composer Ayase and vocalist Ikura, was formed to produce and perform songs based on the website's story specifically. Among their discography, "Yoru ni Kakeru", based on the Monocon 2019's Sony Music Award winners, Mayo Hoshino's Thanatos no Yà «waku (), was a massive commercial success amidst COVID-19 pandemic in Japan in 2020 and established their musical career. The duo and the website later collaborated on another contest Yoasobi Contest for three times. Other musical collaborations include Halca, Omoinotake, Kana Nishino, Adieu, Hitsujibungaku, Tatsuya Kitani, Yama, etc.