FYI, this story have 3 chapter and 1 extra, and the chapter that was posted here is the last chapter for this story so maybe it's a little bit confusing for you guys.
Is this from manga or just an illustration?
http://www.mangago.zone/read-manga/kono_koi_ni_mirai_wa_nai/nbt/d_v-2-chapter-9/pg-29/
Sasaki : Miyano..
Me : kyaaaaa, something serious gonna happen *continue reading**died of sweetness*
⁄(⁄ ⁄·⁄ω⁄·⁄ ⁄)⁄
Spoiler, maybe?
I just read the comment from someone who read the LN, someone said demon lord is kumoko, while the other said she's not kumoko. So i did a little search on google and found out that the demon lord's name is ariel and she's the very fist spider, so i don't think she's our kumoko. But i don't read the LN or WN, so i'm not really sure. Maybe the info i got is wrong.
since you are okay with spoilers, to confirm you can search for MC 'final form' on the wikia of this story.
there are drawing of her evolutions, including futures ones.
compare that with what we saw, and boom you have your answer :)
from there you can also get some detailed trustful spoilers (at least a bit more trustful than conflicting comments).
the link: http://kumo-desu-ga-nani-ka.wikia.com
Thank you (=・ω・=)
http://iweb7.mangapicgallery.com/imgfiles/naruse_akira_to_ikkai_ya_retara_ore_wa_mou_shinde_mo_ii/5/028.png
Boku, Ecchi na Tenshi desu! (Yaoi)
http://www.mangago.zone/read-manga/boku_ecchi_na_tenshi_desu/
Thank you (づ￣ ³￣)づ