Isekai Quartet

Isekai Quartet (異世界かるてっと, Isekai Karutetto) is a Japanese anime series that serves as a chibi-style crossover between the light novel series Kono Subarashii Sekai Ni Shukufuku Wo!, Overlord, Re:Zero kara Hajimeru Isekai Seikatsu and Youjo Senki, all published by Kadokawa Corporation.

The series aired its first season in April 2019 and a second season was confirmed to air in January 14, 2020, including characters from other series such as Tate no Yuusha no Nariagari.

Synopsis
It is a normal day; everyone from deranged military girl Tanya von Degurechaff and 16-year-old isekai protagonist Kazuma Sato to expansionist overlord Ainz Ooal Gown and demon sisters Rem and Ram go on with their daily lives. Suddenly, a conspicuous red button begging to be pressed appears before them. Overcome by curiosity, the otherworldly characters push the button, sending them to an unfamiliar world.

With no way of escaping, the characters must lead a normal school life and make acquaintances with the others. One thing is certain: the classroom full of fan-favorite eccentric personalities never gets boring!

Theme Songs

 * Opening, Season 1: Isekai Quartet (song)
 * Ending, Season 1: Isekai Girls Talk
 * Opening, Season 2: Isekai Showtime
 * Ending, Season 2: Defective! Isekai Theater