The fifth instalment of the Sekai Series.

An alleged prequel to "Kimi to Boku no Kowareta Sekai," when Byouinzaka Kuroneko and Hitsuuchi Samatoki were in middle school.

Note: Two of its chapters were released in Mephisto 2009 Vol. 2/3. Further chapters have yet to be released.
Nisio has mentioned Boku no Sekai in 2020 and...