DMM/FANZA: https://www.dmm.co.jp/dc/doujin/-/detail/=/cid=d_212319/ DLsite: https://www.dlsite.com/maniax/work/=/product_id/RJ344770.html An extra doujinshi chapter to Hero no Himitsu (ヒーローの秘密) by Imamura Youkou (陽子今村) (yes, the romaji of the author's name is wrong on this cover), which can be found translated into English on MangaDex here: https://mangadex.org/title/b4a21b67-22e7-4482-add5-8cd9451bedfe/hero-no-himitsu When I have time and money, I'll get this translated into English like the rest of the series.