The creator of Astrea, Tonari no Botulinus, has said farewell on his pixiv account on the 31st of December 2021, and deleted his account at the start of 2022. T_T
It came to my attention that he updated "Defeated Warrior Append" a while after I posted the gallery here. Fortunately, I was able to obtain a copy of the updated version (with 92 added images), and is thus presented here.
Chapters 01-10 can be found here: /g/1237973/cabd12ad7d/ Chapters 11-18 are here: /g/1367149/f3ed4c1919/ Some hack sniped Chapters 19 & 20 from me, won't link to that gallery. :P (Sorry if it sounded petty, but the same hack tried to snipe another story I upload, though in the end I managed to have his gallery expunged -- maybe it helped that I received the blessing of the original creator.