The official website for the currently airing Tensei shitara Slime Datta Ken
TV anime has announced on Friday that an OVA will be bundled in the eleventh volume of the manga
series, to be released on March 29, 2019. The story will be about a Sumo wrestling competition that will be held in the fantasy world for the first time, as suggested by Rimuru. A special manga by the mangaka Taiki Kawakami
announcing the OVA has also been revealed.
The currently airing anime series has been airing since October 2 and is planned for two-cours. It is based on the manga version, which is serialized via Shounen Sirius
magazine by Taiki Kawakami and Fuse
since March 2015. The tenth compiled volume released today on December 7. Kodansha Comics USA has been publishing the manga in English since August 2017, and the ninth volume is planned for a March 2019 release.
Fuse has been writing the story on the Shousetsuka ni Narou
website between 2013 and 2015. Micro magazine has been releasing the light novel
series with illustrations by Mitz Vah
since 2014, and thirteen volumes have been releases as of September 28. Yen Press has been releasing the light novel series in English under the Yen On imprint since December 2017 and the fifth volume is planned for April 23, 2019 release.
Source: Official Twitter