Re:Zero - The Forbidden Book and the Mysterious Spirit is a browser-based game that is developed by DMM Games, which is scheduled for a 2021 release. It is a free-to-play game with micro-transactions.

The game features a story that is a retelling of the anime, however, the game includes a new original story that was not included in the anime. The story will be supervised by the series' author Tappei Nagatsuki and the character designs will be supervised by the series' illustrator Shinichirou Otsuka. It also features the original voice actors Kobayashi Yuusuke, Takahashi Rie, Minase Inori, Murakawa Rie, Uchiyama Yumi, and more, reprising their roles from the Re:Zero anime and the illustrator from the original light novel series Shinichirou Otsuka to be the illustrator for the game.