Nagatoro got the idea for the nipple guessing game from Love Slave

Ijiranaide Nagatoro-san – RABUJOI – An Anime Blog

April, 2017

Kono Subarashii Sekai ni Shukufuku Wo! 2 – 04 - Random Curiosity

Cherry Blossom Palette: City by the Sea (Ch. 21) by EmtenDew on DeviantArt

uesaka sumire – RABUJOI – An Anime Blog

Ijiranaide Nagatoro-san Chua Tek Ming~*Anime Power*~ !LiVe FoR AnImE, aNiMe FoR LiFe!

Nagatoro got the idea for the nipple guessing game from Love Slave : r/ nagatoro

Ijiranaide, Nagatoro-san - Episode 3 discussion : r/anime

General Content Ratings Thread 2.0: Same Principle, Different Format - Page 2 - Anime & Manga - UnevenEdge