2-episode prequel follows Levi, Erwin

Kodansha Comics announced on Friday that it will release the two-episode original anime DVD (OAD) series Attack on Titan: No Regrets with special editions of Haijime Isayama's main Attack on Titan manga. The first episode will be bundled with the special edition 18th volume in April and the second episode will be bundled with the special edition 19th volume in August. Both sets will retail for US$19.99.

The special edition volume 18 will also have a variant dust jacket drawn by comic book artist Cameron Stewart:

In Japan, the OAD shipped with the 15th and 16th volumes of the manga.

The cast and staff returned from the 2013 television anime adaptation of Hajime Isayama's main manga. They are joined by Koji Yusa (Zettai Karen Children, Black Butler) and Mariya Ise (Yes! Precure 5, Hunter × Hunter) as Farlan and Isabel, respectively.

The OAD adapts the Attack on Titan: No Regrets (Shingeki no Kyojin Gaiden: Kuinaki Sentaku) spinoff manga. Artist Hikaru Suruga and writer Gun Snark launched the two-volume spinoff manga in Kodansha's ARIA magazine in fall 2013, and Kodansha Comics published it in North America. Kodansha Comics describes the story:

This prequel to megahit Attack on Titan answers the questions: How did Captain Levi of the Survey Corps go from street tough to humanity's strongest soldier? And how did Commander Erwin become a cold, calculating leader, ready to sacrifice anything to save the human race? The fires that forged this bond of loyalty and trust were intense indeed!

Kodansha Comics previously released the OAD episode "Isle's Notebook" with English subtitles with the main manga's 17th volume in December.

Update: Corrected Gun Snark's spelling, clarified that the OADs will ship with the main manga, corrected which manga volumes the OADs shipped with in Japan. Thanks, NJ_.