Tensei Shitara Slime Datta Ken: Bangaihen - Toaru Kyuuka no Sugoshikata

Warning: This Spinoff manga has spoilers from the Light Novel.

After successfully completing the Founding Festival, which includes meetings with the leaders of various countries, a martial arts tournament, technology presentations, and the unveiling of the underground labyrinth, the peaceful daily life in Tempest has returned. Then, Veldora begins to say, "I'm also thinking of developing magic beasts", and the three of them, including Rimuru and Hinata, who are interested in developing new magic, head for the Magic Tower, the sacred place of magic...?

This work is based on the Light Novel, and the timeline is from the end of Volume 9 to the beginning of Volume 10.